junior cert science physics booklet

Junior Cert Science Chapters and Test ResultsPage Result Date

Biology1. Living Things2. Cells and the Microscope3. Food4. The Digestive System 5. Respiration and Breathing 6. The Circulatory System7. Excretion8. The Skeletal and Movement9. The Senses and Nervous System10. Human Reproduction11. Genetics12. Photosynthesis and Plant Responses 13. Structure and Transport in Flowering Plants14. Plant Reproduction15. Ecology16. Microorganisms

Chemistry1. States of Matter2. Elements, Compounds and Mixtures3. Separating Mixtures4. The Atom5. Solutions and Crystals6. Water 7. Ionic and Covalent Bonding 8. The Alkali and Alkaline Earth Metals9. Acids and Bases10. The Air and Oxygen11. Carbon Dioxide12. Metals and Non-Metals13. Plastics

Physics1. Measurement, Equipment and Units2. Density3. Velocity and Acceleration4. Force5. Moments6. Centre of Gravity7. Pressure8. Work, Energy and Power9. Sound10. Light11. Heat12. Magnetism13. Static Electricity14. Current Electricity15. Electronics

End of Year ResultsChristmas Summer

First YearSecond yearThird Year Mock Exam:

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Junior Cert Science chapters by year

Biology

First Year Second Year Third Year1. Living Things2. Cells and the Microscope3. Food4. The Digestive System 5. Respiration and Breathing 6. The Circulatory System7. Excretion8. The Skeletal and Movement9. The Senses and Nervous System10. Human Reproduction11. Genetics12. Photosynthesis and Plant Responses 13. Structure and Transport in Flowering

Plants14. Plant Reproduction15. Ecology16. Microorganisms

ChemistryFirst Year Second Year Third Year

1. States of Matter2. Elements, Compounds and Mixtures3. Separating Mixtures4. The Atom5. Solutions and Crystals6. Water7. Ionic and Covalent Bonding 8. The Alkali and Alkaline Earth Metals9. Acids and Bases10. The Air and Oxygen11. Carbon Dioxide12. Metals and Non-Metals13. Plastics

PhysicsFirst year Second Year Third Year

1. Measurement, Equipment and Units2. Density3. Velocity and Acceleration4. Forces5. Moments6. Centre of Gravity7. Pressure8. Work, Energy and Power9. Sound10. Light11. Heat12. Magnetism13. Static Electricity14. Current Electricity15. Electronics

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Physics: 1. Measurement, equipment and unitsPlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOP1 Measure length, mass, time and temperature, and perform simple calculations based on these to find the

derived quantities: area, volume, density.Understand that units of measurement follow the SI system.

OP2 Measure mass and volume of a variety of solids and liquids.

Student Notes

There are literally hundreds of different units for some quantities like length and mass.How different units of length can you think of?It is important for scientists that everybody is using the same units.Can you say why?Scientists use units called S.I. UnitsS.I. stands for Système International d'unités ; it is in french because it was the French who first promoted this system (you don’t need to know this).What do you think Système International d'unités means ?

Length Mass Time Temperature Area Volume SpeedS.I. units metres Kilograms seconds Degrees Celsius Metres

squaredMetres cubed

metres per second

Symbol m kg s 0C m2 m3 m/sEquipment Metre stick,

OpisometerElectronic

balanceClock,

stopwatchThermometer

Other commonly-used units:Mass: grams (g)Area: centimetres squared (cm2)Volume: centimetres cubed (cm3)

1 litre = 1000 cm3

Instruments used to measure the volume of a liquid1. Graduated cylinder2. Pipette3. Burette

To find the volume of a small stoneCarefully drop the stone into a graduated cylinder which already has water in it and note the increase in volume of water.

To find the volume of a large stoneCarefully drop the stone into an overflow can which is already full to the top with water and note the amount of water that it pushes out by placing a graduated cylinder under the spout of the overflow can.

To find the mass of a solid objectThe mass of an object can be found by weighing it using an electronic balance (commonly known as a weighing-scale).

To find the mass of a liquidFirst find the mass of an empty container, then pour the water into it and find the new mass. Subtract to find the mass of the liquid.

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Area of a regular object = length × width

Volume of a regular object = length × width × height

Exam Questions1. [2006 OL]

Find the area of the rectangle drawn on the right using the measurements given.In what unit is the area measured?

2. [2007 OL] (i) What is the name the piece of equipment shown on the right?(ii) Give one use of this piece of equipment.

3. [2007](i) Name the item of laboratory equipment shown in the diagram.(ii) Name a second item of laboratory equipment which enables more accurate measurements of volume to be

made.

4. [2006 OL] [2009 OL](i) The diagram shows a piece of equipment, labelled A, containing water. Name A.(ii) A stone was then added and a new volume was recorded as shown in B.

What was the volume of the stone in cm3?

5. [2008 OL]Name and give one use for the piece of equipment shown in the diagram.AnswerThermometer; it is used to measure temperature

6. [2008 OL, 2006 OL](i) Name the piece of equipment drawn on the right.(ii) Give one use for this piece of equipment.

7. [2008](i) Give one safety precaution taken by the pupil, shown in the photograph, while doing

an experiment in a school laboratory.(ii) Describe a precaution, not shown in the photograph that you would take when heating

a substance in a test tube in a school laboratory.

8. [2009]Name any two items of laboratory equipment shown in the diagram.

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Exam Solutions1. 6 × 4 = 24 cm2

2. (i) Graduated cylinder(ii) To find volume of liquids / measure (amount of) liquids 3.(i) Item shown: Graduated cylinder (ii) Second item: burette/ pipette4.(i) Graduated cylinder (ii) 90 – 75 = 15 cm3

(iii) 15 cm3

5. Thermometer; it is used to measure temperature6.(i) Tripod (ii) To hold (support) objects (when heating) 7.(i) Wearing goggles/ looking through wall (side) of test tube/ tube in holder/ apparatus in centre of bench (ii) Point tube away/ add boiling chips to a liquid/ use small amounts/ lab coat/ heat gently/ screen/ gloves/ tie hair

back… 8. Bunsen burner/ tripod/ pipe clay triangle/ crucible/ tubing/ evaporating dish

Other Test Questions

1. What is the unit of (i) Length, (ii) Time, (iii) Mass, (iv) Area, (v) Volume?

2. What instrument would you use to measure (i) the length of a curved line, (ii) diameter of a marble?

3. Name two instruments used to measure weight.

4. What is an opisometer used for?

5. Name two instruments used to measure mass.

6. Name two instruments used to measure volume of a liquid.

7. Name an instrument used to measure the altitude of a mountain climber.

8. Name an instrument used to measure the distance by road between two locations on a map.

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Physics: 2. Density

Please remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOP2 Measure mass and volume of a variety of solids and liquids and hence determine their densities.

Student NotesWe learned how to measure the mass and volume of objects in a previous chapter. To measure density we simply use the following formula:

The unit of density is the kg/m3 (pronounced “kilogram per metre cubed”) or g/cm3

Mass, Volume and Density: Exam questions1. [2008 OL] (i) Complete the equation in the box below using the words on the right.

Density =(ii) If the mass of a stone is 20 g and the volume of the stone is 10 cm3, find the density of the stone.

2. [2007 OL] A block of metal has the measurements shown on the right.The mass of the metal block is 21 g.

(i) Write the letter V beside the value of the volume of the block.(ii) Write the letter D beside the value of the density of the block.

3. [2009 OL]The mass of a metal block is 14.7 g. It has a volume of 7 cm3.

(i) Name the instrument you would use in the laboratory to find the mass of the block.

(ii) Write the letter D beside the value of of the density of the block.(iii) Write the letter U beside the unit used to measure the density.

4. [2009]A pupil measured the volume of a potato using the items of laboratory equipment, labelled A and B as shown in the diagram.

(i) Name the items labelled A and B.(ii) The potato had mass 175 g and volume 125 cm3.

Calculate the density of the potato.Give the units of density with your answer.

(iii) Why did the potato sink in the water?

5. [2007]Ice floats on water but ice sinks in ethanol (an alcohol).Use this information to compare the density of ice with

(i) the density of water; (ii) the density of ethanol.

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MASSVOLUME

8 cm3

10 cm3

2.1 g cm–3

210 g cm–3

2.1102.9cm3

g/cm3

Mass

Density × Volume

Exam Solutions1. (i) Density = Mass / Volume(ii) Density = 20 /10= 2 g/cm3

2. (i) V: 10 cm3 (ii) D: 2.1 g cm-3 3.(i) Electronic balance / weighing scales(ii) Density = 14.7÷7 = 2.1 (iii) Unit = g/cm3

4.(i) Item A is an overflow can

Item B is a graduated cylinder(ii) Density = 175/125 = 1.4 g/cm3

(iii) Because it is denser than water5.(i) Ice is less dense than water (ii) Ice is more dense than ethanol

Other Test Questions1. What is meant by the term ‘density’?

2. What is the formula used to calculate the density of an object?

3. What are the units of density?

4. Draw a diagram of the apparatus used to measure the density of an irregular-shaped object?

5. Describe with the aid of a diagram an experiment to measure the density of an irregular object.

6. Describe with the aid of a diagram an experiment to measure the density of a liquid.

7. A stone has a mass of 120 g and a volume of 20 cm3, what is the density of the stone?

8. The density of Iron is 8 g/cm3. Calculate the mass of 6 cm3 of Iron.

9. What is the density of an object which has a mass of 20 kg and whose volume is 4 m3?

10. Draw a diagram of the apparatus used to measure the density of an irregular-shaped object?

11. A student measured the density of a number of substances. The results are shown in the table below.

Substance Density (g/cm3)

Cork 0.3

Polystyrene 0.03

Water 1.0

Paraffin Oil 0.7

Rubber 1.1

Identify two substances that would float in paraffin oil.

12. Why can a solid like ice float on water?Physics: 3. Velocity & Acceleration

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SyllabusOP1 Perform simple calculations based on speed, velocity, and acceleration

Student NotesSpeedSpeed = distance ÷ by timeThe unit of speed is the metre per second (m/s).

VelocityVelocity is much the same as speed, except when we talk about velocity we usually include a direction, e.g. the velocity of a car is 10 m/s heading East.

The slope of a distance-time graph corresponds to the velocity of the object.

AccelerationAcceleration = velocity ÷ by timeThe unit of acceleration is the metre per second squared (m/s2).

Consider an object which is speeding up as it is moving. Its velocity after one, two, three and four seconds is given in the following table:

Time Velocity1 second 10 m/s2 seconds 20 m/s3 seconds 30 m/s

We can see that with every second that passes the velocity increases by 10 m/s.Alternative ways of writing this are the velocity increases by 10 m/s per second, the velocity increases by or 10 (m/s)/s the velocity increases by 10 m/s2 Instead of saying that ‘the velocity increases by 10 m/s per second’, we simply say that ‘the acceleration is 10 m/s2’.

Problem: A sports car can go from 0 to 300 m/s in 10 seconds. Calculate the accelerationAnswer:

The slope of a speed-time graph corresponds to the acceleration of the object.

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Distance

Speed × Time

Exam Questions1. [2009]

Define velocity.

2. [2007 OL]The speed of a car is 15 m s–1.

(i) In the table write the letter D beside the distance the car will travel in 5 seconds.(ii) Write the letter F beside the word that describes what happens when the speed of a car

increases.

3. [2009 OL](i) A cyclist moves 20 metres along a track in 4 seconds.

In the table write the letter S beside the speed of the cyclist.(ii) Write the letter D beside the distance the cyclist will travel in 2 seconds.

4. [2008 OL] A cyclist moved along a track.The distance travelled by the cyclist was measured every 2 seconds.The data collected is presented in the table below.

(i) Use this data to draw a graph of distance travelled (y-axis) against time (x-axis) using the grid provided below.(ii) Use the graph to estimate the distance travelled by the cyclist in 5 seconds. (iii) Calculate the speed of the cyclist in m s–1 (m/s).

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3 m75 mAccelerationForce

5 m/s80 m/s10 m40 m

Distance travelled (m) 0 10 20 30 40Time (s) 0 2 4 6 8

5. [2009]A stone was dropped from the top of a tall cliff. The stones approximate velocity was measured each second as it fell. The data collected during this experiment is given in the graph.Use data from the graph to estimate the acceleration of the stone as it fell. Give the units of acceleration with your answer.

Exam Solutions1. Velocity is defined as the rate of change of displacement with respect to time.2.(i) D: 75 m(ii) F: Acceleration 3.(i) S: 5 m/s(ii) D: 10 m4.(i) Correct line going through the origin (ii) 25 m (iii) The speed corresponds to the slope of the graph = 5 m/s 5. The acceleration corresponds to the slope of the graph = 10 m/s/s or m s-2 or m/s2

Other Test Questions1. Define Velocity.

2. Define Acceleration.

3. What is the formula for calculating speed?

4. What is the unit of speed?

5. Calculate the velocity of a swimmer who swims 100 m in 20 secs.

6. Calculate the velocity of a teacher who runs 150 m in 30 seconds.

7. How long does it take a girl to travel 1000 m, if her speed is 2 m/s?

8. How long does it take a person to travel 1000 m, if their velocity is 20 m/s?

9. What are the units of acceleration?

10. One car can go from 0 to 100 m/s in 10 seconds while another car which can go from 100 m/s to 150 m/s in 3 seconds. Which car has the greater acceleration?

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Physics: 4. ForcePlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOP4 Understand the concept of force, recall that the newton is the unit of force, and describe forces and their

effects

OP5 Investigate examples of friction and the effect of lubrication

OP6 Investigate the relationship between the extension of a spring and the applied force

OP7 Understand that weight is the force of gravity and that weight varies with location; recall that mass in kilograms multiplied by 10 is approximately equal to weight in newtons on the surface of the earth.

Student Notes

The newton (symbol N) is the unit of force.

Forces can be measured using a spring-balance (the proper name is a newton-meter).

Friction

Friction can be a nuisance (e.g. it slows things down when you don’t want it to when driving a car or riding a bike).Friction can also be useful (e.g. brakes on a bike, and to enable us to walk).

Experiment: To demonstrate friction and how a lubricant can be used to reduced friction.Attach a spring balance to a wooden block and use it to pull the block over the bench. Note the reading on the spring-balance.Now put some oil or grease under the block and repeat. Notice that the force required to pull the block is much less.

Weight and MassMass is a measure of the amount of matter (“stuff”) in something.The weight of an object is a measure of the gravitational pull on it.

The mass of an object doesn’t change from one place to the next because it still has the name amount of stuff inside (the same number of atoms), but the weight of the object will be much less on a planet smaller than Earth (or on the moon) while it will weigh much more (it will be much ‘heavier’) on a bigger planet. In fact if you could go to one of the bigger planets you would not even be able to stand up because you weigh so much!

Maths Problems

e.g. a student of mass 60 kg has a weight of 600 N.

Note: There are 1000 grams in a kilogram (kg).

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A force is something that causes an object to change velocity or accelerate.

Friction is a force that opposes motion between two objects in contact.

Weight is a force (due to gravity)

Weight (in newtons) = Mass (in kilograms) × 10

Hooke’s Law

Experiment: To investigate the relationship between the extension of a spring and the force that is stretching it.1. Use a newton-meter to stretch a spring and note the extension and the force used.2. Repeat for lot of different forces.3. Plot a graph of force used against extension.4. Result: You should find that the graph is a straight line.5. Conclusion: The graph is a straight line which shows that the extension increases at a constant rate

with the applied force.

Exam questions1. [2007 OL]

Different units are used to measure different physical quantities.(i) In the table on the right write the letter L beside the unit of length.(ii) Write the letter W beside the unit of weight.

2. [2009 OL]Friction can be useful when driving a car.

(i) Name one way in which friction is useful when driving a car.(ii) Name one possible way to reduce friction.

3. [2006 OL] Friction is an example of a force.

(i) Give another example of a force.(ii) Give one way to reduce friction. (iii) After what scientist is the unit of force named?

4. [2008]The globular cluster shown is a group of stars (like a small galaxy). Gravity is the force that holds the stars together in this formation.Give two effects that gravity has on your everyday life.

5. [2009](i) A stone was dropped from the top of a tall cliff. Name the force that causes the stone to fall downwards. (ii) The stone had a mass of 2 kg. What was the weight of the stone on earth? Give the unit.

6. [2006]A pupil measured the weight of an apple of mass 0.2 kg using a spring balance and got a reading of 2 N. Distinguish between weight and mass.

7. [2006]State Hooke’s law.{This isn’t on the syllabus and shouldn’t have got asked, so presumably won’t appear again – but you never know}Robert Hooke (1635-1703) made a number of discoveries including the effect of force on elastic bodies now known as Hooke’s law.

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MetreNewtonJoule

The extension of a stretched string depends on the force that is stretching it.

8. [2006 OL] A student carried out an investigation to examine the relationship between the extension (increase in length) of a spring and the force applied to it.The diagram shows the apparatus used.The table shows the data collected by the student.

(i) Describe how the student could have taken any one of these measurements.

(ii) Draw a graph of the extension (y-axis) against the force in the grid provided on the right.

(iii) What force results in a 6 cm extension of the spring?

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Force (N) 0 2 4 6 8Extension (cm) 0 4 8 12 16

9. [2006]A student was given a box of identical springs and asked to analyse them so that they could be used as newton meters. The student performed an experiment, using the apparatus shown in the diagram, on one of the springs.In the experiment the student measured the increase in length of the spring caused by a number of weights. The spring was tested to destruction (that is weights were added until the spring was damaged).The data from the experiment is given in the table.

(i) Plot a graph of extension (increase in length – y-axis) against weight (x-axis) in the grid provided.

(ii) Use the graph to find the weight that would produce an extension of 5 cm in the spring.

(iii) Study your graph carefully.The spring obeys Hooke’s law for the earlier extensions and then when the spring becomes damaged it does not appear to do so.Estimate, from your graph, the weight after the addition of which the law seems no longer to apply.

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Weight (N) 0.0 0.4 0.8 1.2 1.6 2.0 2.4Extension (cm) 0.0 2.0 4.0 6.0 8.0 8.5 8.6

10. [2009 OL]A student investigated the relationship between the extension of a spring and the force applied to it.The equipment shown in the diagram was used.The data collected is shown in the table.

The student then drew the graph shown.Answer the questions that follow about this investigation.

(i) Name an instrument used to measure the force in this investigation.(ii) Describe how the student could have measured the extension of the spring.(iii) What conclusion would you draw from this investigation?

Exam Solutions1. (i) L: Metre (ii) W: Newton 2.(i) Grip / traction / road holding / stopping(ii) Oiling / waxing / greasing / polishing / lubricants / bearings3. (i) Gravity / weight / push / pull / magnetic / electric / twist (ii) Oiling / lubrication / wax / polish / ball bearings (iii) Newton4. It gives things weight/ it keeps things on the surface of the earth/ it causes things to fall… 5.(i) Gravity(ii) Weight = mass × 10 = 2 × 10 = 20 N( Newtons)6. Weight is a force which is caused by gravitational pull.

Mass is a measure of the amount of matter in something.7. The extension of a stretched string depends on the force

applied to it.8. (i) Add (hang) weights onto the string and measure the

extension using the metre stick (ii) Plot all the points and draw a straight line.(iii) 3 N 9.(i) See graph

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Force (N) 0 2 4 6 1. 8Extension (cm) 0 4 8 12 2. 16

(ii) Weight = 1.0 N (accept range 0.9 to 1.1) (iii) 1.6 N (accept range 1.6 to 2.0) 10.(i) Spring balance / Newton meter (ii) By using a ruler or a metre stick (iii) Extension is proportional to force applied / as force is increased the extension increases at the same rate.

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Other Test Questions1. What is meant by the term ‘force’?

2. What is meant by the term ‘friction’?

3. Give an example of how friction can be useful on a bicycle?

4. Give an example of how friction can be a nuisance on a bicycle?

5. How might a cyclist reduce friction?

6. Give another example of how friction can be useful.

7. Give another example of how friction can be a nuisance.

8. Describe how you would investigate the effectiveness of two different lubricants. Include reference to a control. Give three ways of making sure that you carry out a fair test.

9. What is meant by the term ‘mass’? What is the unit of mass?

10. What is meant by the term ‘weight’? What is the unit of weight?

11. Name two instruments used to measure weight.

12. Calculate the weight (in Newtons) of a bag of sugar, which has a mass of 500 grams.

13. A man has a mass of 100 kg. What is his weight?14. Would the man weigh less, more or the same on the moon?15. Why does the man have a different weight on the moon?16. What will be the mass of the man on the moon?17. How would you be affected if your weight suddenly doubled?

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Physics: 5. MomentsPlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOP9 Investigate the law of the lever; recall two everyday applications of levers

Student Notes

Everyday applications of leversSeesaw, scissors, door handle, wheel-barrow, spanner, etc.(Can you identify the fulcrum in each case?)

ExampleA force of 75 N is used to turn the spanner in the diagram. If the distance between the force and the nut is 10 cm calculate the moment of the force.AnswerMoment = Force x distance

= 75N × 0.1 m=7.5 N m

What would be the effect of using a longer spanner?

The Law of the Lever:

Experiment: To Verify the Law of the Lever

Procedure:1. Hang a metre stick from the 50 cm mark as shown.2. Attach two weights and adjust their positions until the metre stick balances.3. Note the position and force of each object.4. Show mathematically that the force multiplied the distance clockwise equals the force multiplied by the distance

anti-clockwise.

Maths ProblemsLaw of the Lever questions

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A lever is a rigid object which is free to turn about a fixed point called a fulcrum.

The Moment of a force = the force × distance (between the force and the fulcrum).

When a lever is balanced, the clockwise moment acting on it is equal to the anti-clockwise moment acting on it.


Give an everyday example of an application of the lever, using a labelled diagram, showing the fulcrum and at least one force acting on the lever.

2. [2008 OL]The crowbar in the diagram acts as a lever and applies a turning force on the boulder (large rock).Answer the questions which follow with reference to the points A, B and C in the diagram.

(i) Which of the three points, A, B or C, is the fulcrum (the point about which the turning force acts)?

(ii) At which of the three points, A, B or C, will the least force be needed to move the boulder? Give a reason for your answer.

3. [2008]State the law of the lever.

4. [2007]Define moment of a force.

5. [2007]The diagram shows a metre stick suspended from its centre of gravity.A force of 3 N acts on the stick at the 90 cm mark and a force of F newtons acts on the stick at the 20 cm mark. The metre stick is balanced horizontally.Calculate force F.

Exam Solutions

1. See diagram2.(i) The fulcrum is at the point C. (ii) A, because the lever is longest at this point.3. When a lever is balanced the clockwise moment (turning effect) equals the anticlockwise moment.4. Moment of a force is equal to the force multiplied by the distance between the force and the fulcrum.5. 30 × F = 40 × 3

F = 4 N Other Test Questions

1. What is a lever? 2. Give two examples of a Lever3. Define the term ‘Moment of a Force’.4. A wrench 30 cm long is used by a mechanic to turn a nut. If the force he exerts on the end is 5 Newtons, calculate

the moment of the force.5. State the Law of the Lever6. A boy held a book of weight 50 Newtons in his fully outstretched hand, at a distance of 50 cm away. Calculate the

moment of the force.7. A wrench 50 cm long is used to turn a nut. If the force exerted on the other end of the wrench is 20 N calculate the

moment of the force.8. List two ways in which an object can be made more stable.9. Draw a diagram of a scissors and indicate where the fulcrum is.10. Beyonce weighs 500 N and is sitting at one end of a see-saw which is 4 m long and balanced in the middle. Jordan

is 2000 N. Where should she sit in order to balance the see-saw?11. A metre stick is balance in the middle and has a force of 8 N hanging from the 20 cm mark. What force needs to

hang from the 60 cm mark in order to balance the metre stick?

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Physics: 6. Centre of GravityPlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

Syllabus OP8 Find the centre of gravity of a thin lamina

Investigate the role of centre of gravity in design for stability and equilibrium

Student Notes

Expt: To find the centre of gravity of a sheet of cardboard.1. Set up as shown.2. Draw a line to represent the position of the cord.3. Rotate the sheet of cardboard and repeat.4. The intersection of the two lines represents the centre of gravity of the object

StabilityAn object can be made more stable by:(i) giving it a low centre of gravity(ii) giving it a wider base

DemonstrationTry to balance an empty coke can on its lip – it can’t be done because the centre of gravity is not over the lip.Now pour a little water into the coke can and try again. This time you should be able to balance it because the water results in the can having a new centre of gravity which is now directly over the lip.

Be able to answer all questions from this chapter in the workbook and textbook

Test Questions

1. Define the term ‘Centre of Gravity’.

2. When is an object in stable equilibrium?

3. Give two ways in which an object can be made stable.

4. What factor determines whether an object which has been tilted will fall over?

5. Describe briefly how to find the exact centre gravity of an irregular-shaped piece of cardboard (make sure you include a diagram in your answer).

6. Explain why the centre of gravity of a double-decker bus should be as low as possible.

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The Centre of Gravity of an object is the point through all the weight of the object appears to act.

An object will topple if a vertical line through its centre of gravity falls outside its base.

Physics: 7. PressurePlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOP10 Understand the relationship between pressure, force and area; perform simple calculations using this

relationship

OP11 Investigate the relationship between pressure and depth for a liquid

OP12 Show that air has mass and occupies space

OP13 Understand that the atmosphere exerts pressure and that atmospheric pressure varies with height

OP14 Examine weather charts to observe variations in atmospheric pressure and relate these to weather conditions

Student Notes

Pressure is caused by a force that pushes against an object.The pressure increases when the force increases or when the area (that the force is acting on) decreases.

The unit of pressure is the pascal (Pa).You can also use the N/m2 or N/cm2.

Example 1:The wind exerts a horizontal force of 1000 N on a wall of area 20 m2. Calculate the pressure at the wall.Answer: P = F ÷ A = 1000 ÷ 20 = 50 pascals.

Example 2:A lady weighs 800 N and is standing in a pair of stiletto heels, each of area 2 cm2.An elephant weighs 27000 N and the total area of its feet is 1800cm2.Which exerts more pressure on the ground – the lady in stilettos or the elephant?AnswerTotal pressure exerted by the lady’s (two) feet = 800 ÷ 4 = 200 N/cm2

Total pressure exerted by the elephant’s (four) feet = 36000/1800 = 20 N/cm2

The lady exerts ten times more pressure on the ground than the elephant.

DemonstrationSet up as shown. The water coming out of the bottom hole travels the farthest, because it is under the greatest pressure.

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Pressure in Liquids: the pressure in a fluid increases with depth.

Force

Pressure × Area

DemonstrationWeigh an empty plastic bottle (with the top on) and note the mass.Pump air into it using a special pump and weigh it again. Note the new mass.Result: there was an increase in mass as a result of pumping air in, therefore air has mass.

DemonstrationGlue some cotton wool to the bottom of a glass (inside).Turn the glass upside down, submerge it completely into a large bowl of water and then remove it again.Notice that the cotton wool is still dry.Conclusion: the water could not enter the glass because there was air already in there.

The atmosphere is made up of giggling atoms and exerts a huge amount of pressure on all objects, including the earth.DemonstrationUse a large metal drum and pump the air out using a vacuum pump. The drum will collapse (implode) because there is now a greater pressure outside acting inwards than there is inside acting outwards.

Atmospheric pressure decreases as the height above sea level increases (because there is less air overhead).

Areas of high atmospheric pressure are represented on a weather chart by the letter H and will normally have dry, clear, settled weather.Areas of low atmospheric pressure are represented on a weather chart by the letter L and will normally have cloudy, windy, wet weather.

Why is low atmospheric pressure associated with bad weather?Low atmospheric pressure means that it is easy for water to evaporate into the air (because the ‘blanket’ of atmospheric pressure pressing down on the water is lighter)This results in more clouds and therefore more rain.

We will see when we study the chapter on Heat that water boils at 100 0C at atmospheric pressure. Can you guess why it will boil at less than 100 0C if the atmospheric pressure is low?

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Air has mass

Air occupies space

The atmosphere exerts pressure

Atmospheric pressure varies with height

Atmospheric Pressure and the weather

A barometer measures atmospheric pressure

Exam Questions1. [2006 OL](i) Complete the equation in the box using the words on the right.(ii) Name the piece of equipment used to measure pressure.

2. [2009 OL]Answer the following questions about pressure.(i) Complete the equation in the box below using the words on the right.Pressure =(ii) If a metal block applies a force of 20 N on an area of 5 cm2, find the

pressure being applied by the block.

3. [2009 OL]The diagram shows a container with three spouts. The container is filled with water.Jets of water pour out of the spouts. Why does the jet of water from the bottom spout travel the furthest out from the container?

4. [2007]The diagram is an Atlantic weather chart.(i) Use the chart to predict two weather conditions that you might expect for

Ireland.(ii) Explain why low atmospheric pressure causes one of the weather

conditions that you have given.

5. [2009]The diagram shows a model of the human breathing system.(i) Name the part of the breathing system represented by the

balloons.(ii) Choose from the list on the right the correct word to complete the sentence

below.The part of the breathing system represented by the bell-jar is the ______________ .

Exam Solutions1.(i) Force on top and Area on the bottom(ii) Barometer 2.(i) Pressure = Force ÷ Area(ii) Pressure = 20 ÷ 4 = 5 Pa3. Pressure increases with depth so the water at the bottom is under the greatest pressure.4.(i) Any two from: cloudy/ windy/ rain… (ii) Any one from: air rises/ air moves in/ water vapour condenses (cools)5.(i) The lungs(ii) The rib cage

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AreaForce

AreaForce

Rib cageDiaphragm


1. Calculate the pressure exerted by an object of weight 27N on the ground, if the area of its base is 3m2.

2. Draw a labelled diagram of the set-up used to demonstrate Atmospheric Pressure.

3. Complete the sentence; Pressure increases with ___________.

4. What is the relationship between weather and Atmospheric pressure?

5. Name an instrument used to measure atmospheric pressure.

6. Calculate the pressure exerted on the floor by a wooden box, which weighs 48 Newtons if the dimensions of the base of the box are 2m by 4m.

7. An army tank can travel across wet land if it has tracks on, but not if it is on wheels. Explain why.

8. Draw a labelled diagram of the apparatus you would use to show that pressure in a liquid increases with depth. Include in the diagram the results you would expect to see.

Pressure and boiling point

9. How would you demonstrate that pressure affects boiling point?

10. What is the effect of increased pressure on the boiling point of water

11. Why does increased pressure affect the boiling point of water?Can you think of an application of this (a device which is built on this principle)?Can you think of anyone where this might be a problem?

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Physics: 8. Work, Energy and Power


SyllabusOP15 Define and give the units for work, energy and power, state the relationship between work and power, and

perform simple calculations based on this relationship

OP16 Classify sources of energy as renewable or non-renewable

OP17 State the principle of conservation of energy

OP18 Explain why the sun is considered our primary source of energy and how this is important in food production and energy supply

OP19 List the advantages and disadvantages of different energy sources, including nuclear sources of energy, as part of the solution to national energy needs

OP20 Identify different forms of energy and carry out simple experiments to show the following energy conversions:a. Chemical energy to electrical energy to heat energyb. Electrical energy to magnetic energy to kinetic energyc. Light energy to electrical energy to kinetic energy

OP21 Give examples of energy conversions from everyday experience.

Student Notes

WorkThe unit of work is the joule (J).

EnergyThe unit of energy is also the joule.

Power

The unit of power is the watt (W)

The sun is our primary source of energy.This means that almost of our energy came about either directly or indirectly from the sun. For example fossil fuels were formed from decaying plants and animals.These plants and animals relied on the sun either directly (plants) or indirectly (animals eat plants or other animals that ate plants) for their survival. So essentially, fossil fuels contain the captured energy of the sun from millions of years ago.

Sources of Energy: renewable and non-renewableEnergy sources can be divided into two groups – renewable and non-renewable.

A renewable source of energy can be replenished in a short period of time.

A non-renewable source cannot be replenished in a short period of time.

Examples of renewable sources are solar energy, wind energy, wave energy etc (see table below)Examples of non-renewable energy are fossil fuels (peat, coal, oil etc) which can take millions of years to form.

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Work done = Force × distance

Energy is the ability to do work

Power is the rate at which work is donePower

Energy × Time

Non-renewable energy sources

In Ireland 90% of electricity is generated by burning fossil fuels compared to other European countries that have an average of 50% use of fossil fuels and a 30% use of fossil fuels in the USA.

Renewable energy sources

Conservation of energy

Energy Conversions

The most useful form of energy is electrical energy. This is because it can be changed into other forms easily, e.g. electric to motor to move things, electric to heat, electric to sound, electric to light.

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Original source Advantages Disadvantages

Fossil fuels Fuel can be stored.Relatively cheap.

Increases greenhouse effect. Limited supply of fuel available.

Nuclear energy Very little greenhouse gas emissions.You can get a lot of energy from a very small amount of fuel.

Possibility of nuclear accidents.Not easy to dispose of the waste.

Original source Advantages DisadvantagesSolar energy Costs little to run Expensive to install first day

Not always availableWind energy Costs little to run Expensive to install first day

Not always availableHydroelectric energy Costs little to run Expensive to install first day

Wave energy Costs little to run Expensive to install first dayNot always available

Tidal energy Costs little to run Equipment can be damaged in stormsBiomass energy Costs little to run Requires a lot of land

Geothermal energy Costs little to run Expensive to install first day

Appliance Energy ConversionElectric heater Electricity to Heat

Speaker Electricity to SoundLight-bulb Electricity to Light

The principle of conservation of energy states that energy cannot be created or destroyed, but can only be converted from one form to another.

Potential Energy and Kinetic EnergyAnother way of understanding energy is to divide energy up into two separate categories: potential energy and kinetic energy.Potential energy is energy that is stored, i.e. the energy can do work if released.Examples of potential energy are a stretched string, water at the top of a dam and chemical energy in a battery.

Kinetic energy is energy that is associated with movement, i.e. anything that is moving has kinetic energy.

a. Chemical energy to electrical energy to heat energyAn electric circuit consisting of a battery connected to a light-bulb or heater.Switch on the circuit and note the temperature rising using a thermometer.

b. Electrical energy to magnetic energy to kinetic energyUse an electromagnet (a coil of wire wrapped around a nail, connected to a battery) to pick up some nails.

c. Light energy to electrical energy to kinetic energyConnect a solar panel to an electric motor which turns when light shines on the solar panel

Be able to answer all questions from the textbook and the workbook.

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Experiments


Energy cannot be created or destroyed but it can be changed from one form to another e.g. chemical energy can be converted into heat energy.Describe an experiment you could carry out to show the conversion of chemical energy to heat energy.Draw a labelled diagram of any equipment used.

2. [2008 OL]The diagram shows a common light bulb.Complete the table below by writing the letter B beside the two main energy changes that take place when the bulb is in use.

3. [2006 OL] Give an example from everyday life where electrical energy is converted to kinetic energy.

4. [2009]Give two useful energy conversions that occur when the drill shown in the diagram is being used.

5. [2008]Fill in the missing words in both sentences.

(i) The stretched rubber chord has ______________ energy.(ii) If the stone is released it will have ____________ energy.

6. [2007]When work is done energy is converted from one form to another.Identify one energy conversion that occurred when a car brakes.

7. [2008 OL]In the table write the letter R beside two forms of renewable energy.

8. [2009 OL]In the table write the letter N beside two forms of non-renewable energy.

9. [2007 OL] [2007]Nuclear energy could be used to solve Ireland’s energy shortage.Give one advantage and one disadvantage of using nuclear energy to generate electricity.

10. [2008]The Pelamis, shown in the photograph, converts the energy of waves in seas into electrical energy.Give one advantage and one disadvantage of generating electrical power in this way.

11. [2009]Give one advantage or one disadvantage of fitting solar panels to your home?

12. [2006]Suggest two alternative sources of energy (instead of fossil fuels) for the generation of electricity in Ireland.

13. [2008](i) Name the energy from the sun that the solar panel changes into electricity.(ii) The electrical energy is then changed into a form of energy that can be stored in a

battery Name the form of energy that can be stored in a battery.(iii) In winter it may be dark when the pupils are going to or coming from school.

Give two energy conversions that occur to produce the flashes of light warning motorists approaching the school on dark mornings.

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Electrical to lightElectrical to soundElectrical to heatChemical to heatHeat to light

OilWindSolarCoalWave

CoalOilSolarTidal

14. [2007]The driver of a moving car applied the brakes. The brakes produced an average stopping force of 8 kN (8000 N) and the car stopped having travelled 20 m after the brakes were applied. Calculate the work done in stopping the car.

15. [2006]A girl of mass 60 kg (weight 600 N) climbed a 6 m high stairs in 15 seconds.Calculate the work she did and the average power she developed while climbing the stairs.

Exam Solutions1. Nut (some combustible material) ignited / lighting Bunsen burner

Heating something (e.g. beaker of water) Method of detecting (proving that it is) heating e.g. thermometer OR Circuit containing battery and heating coil (bulb)Heating something e.g. container of waterMethod of detecting (proving that it is) heating e.g. thermometer (bulb feels hot)

2. B: Electrical to light / electrical to heat / heat to light 3. Electric car / Drill/ Device containing electric motor 4.(i) Electrical (electric) to magnetic (ii) Magnetic to kinetic 5.(i) Potential/ stored (ii) Kinetic 6. Kinetic to heat/ kinetic to sound.7. R: Any two of: Wind / solar / wave 8. Coal and oil9. Advantage: no ‘greenhouse gas ‘emissions/ no carbon dioxide (CO2) emissions/ can produce large amounts of

energy/ cleaner supply of electricity.Disadvantage: devastation if a reactor erupts/ very long term storage of wastes/ wastes are radioactive (dangerous).

10. Advantage: renewable/ no pollution/ does not increase global warming/ secure energy source. Disadvantage: energy of waves can vary/ storms could damage the device.

11. Advantage: to reduce fuel bills/ reduce CO2 emissions/ renewable/ ... Disadvantage: expensive/ less heat absorbed in winter (on cloudy days)...

12. Biomass/ nuclear/ geothermal/ solar/ tidal/ wave/ wind/ hydroelectric 13.(i) Light or solar energy(ii) Chemical(iii) Chemical to electrical, Electrical to light 14. Work (= force × distance) = 8000 × 20 = 160000 J15. Work (= force × distance) = 600 × 6 = 3600 J.

Power (= work/time) = 3600/15 = 240 W.

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Energy Questions1. Define the term ‘work’.

2. What are the units of work?

3. Define the term ‘energy’.

4. What are the units of energy?

5. Define the term ‘power’.

6. What are the units of power?

7. A force of 20 N was used to pull a sofa 3 metres across a room. How much work was done?

8. If the time taken in the previous question was 10 seconds, calculate the average power.

9. A weight-lifter lifted a weight of 1000 N a distance of 1.5 metres. How much work was done?

10. If the time taken in the previous question was 2 seconds, calculate the average power.

11. State the principle of conservation of energy.

12. What is meant by non-renewable energy?

13. Name a source of non-renewable energy?

14. What type of energy generates lightning?

15. State the principle of conservation of energy.

16. Write down two useful changes that occur when a hairdryer is in use.

17. What is nuclear energy?

18. State one advantage and one disadvantage of nuclear energy.

19. Why is electricity a convenient form of energy?

20. What is kinetic energy?

21. Give an example of electrical energy being converted to kinetic energy.

22. Name one renewable energy source that can be used in Ireland.

23. Why is this source considered to be renewable?

24. Give two ways of increasing the energy efficiency of a house.

25. Draw a diagram of an experiment to demonstrate electrical energy being converted to magnetic energy and in turn to kinetic energy.

26. Describe how to make a electromagnet.

27. Give two ways of increasing the strength of an electromagnet.

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28. Complete the table.Energy Conversion Example

Kinetic to Heat Rubbing your hand along a desk

Chemical to Heat

Potential to Sound

Light to Electric

29.

instrument List two Energy conversionsElectric drill

Solar panel

Hair dryer

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Physics: 9. SoundPlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopierSyllabusOP40 Show that sound is a form of energy, and understand that sound is produced by vibrations

OP41 Show that sound transmission requires a medium and that echoes are reflected sound

OP42 Understand that the ear detects sound vibrations and that exposure to very loud sounds can cause damage to hearing

OP43 Recall that the speed of sound is less than the speed of light

OP44 Explain the time lag between seeing and hearing the same event

Student Notes

To show that sound is a form of energy you must be able to show that it can do work (because energy is the ability to do work). Work is done when an object is being moved. So we need to show that sound can move something.DemonstrationHang a balloon in front of a speaker; note that when the speaker is turned on the balloon moves.

DemonstrationFeel the speaker vibrate by putting your hand on it. Notice that as the sound gets louder the vibrations get bigger.

DemonstrationNotice that you can see and hear the bell ringing before the vacuum pump is switched on.After pumping the air out you can still see the bell ringing but can no longer hear it.

Echoes occur when sound reflects from a surface back into your ears.

There are tiny hairs in your ear which vibrate when they detect sound and this then gets converted to electrical signals which travel to the brain.

This is why people who work with loud machinery need to wear ear protectors.

The speed of sound is about 340 m/s while the speed of light is about one million times faster. This is why when something far away makes a sound we can see it before we hear it, e.g. in an electrical storm we see the lightning before we hear the thunder.

Maths problems: Speed = Distance ÷ TimeNote that if we are dealing with echoes from a wall, the distance the sound travels will be twice the distance between the source of the sound and the wall.

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Sound is a form of energy

Sound is produced by vibrations

Sound requires a medium

Echoes are reflected sound

The ear detects sound vibrations

Ultrasound is a high-pitched sound beyond the range of the human ear

The speed of sound is less than the speed of light

Exposure to very loud sounds can cause damage to hearing

Exam Questions1. [2007 OL][2009 OL]

A student set up the following experiment to investigate how sound travels through air.An electric bell was placed inside a bell-jar as shown in the diagram.The bell rang and it could be heard clearly.When the pump was switched on it started to pump the air out of the bell-jar and a vacuum was created.At that stage the bell could no longer be heard but it could still be seen ringing.

(i) What conclusion could be drawn from this investigation? (ii) When the air was pumped out, the bell could still be seen even though it could not

be heard. What difference between light and sound does this show? (iii) During an electric storm lightning is usually seen before thunder is heard.

What does this tell us about light and sound?

2. [2007]Describe, using a labelled diagram in the box, an investigation you could carry out to show that sound requires a medium in which to travel.

3. [2007][2008 OL]The picture shows a flash of lightning.

(i) Which is detected first, the flash of lightning or the clap of thunder?(ii) What does this tell us about the speed of light?

4. [2006] [2009]How are echoes produced?

5. [2009 OL](i) The soldier in the diagram has safety goggles on his hat.

Give one reason why safety goggles should be used in the laboratory. (ii) The sign on the right is found displayed at shooting ranges and in many

factories. What instruction does this sign give?(iii) Why is it important to obey the instruction given by this sign?

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Exam Solutions1.(i) Sound will not travel through a vacuum / sound needs a medium to travel.(ii) Light can travel through a vacuum / light doesn’t need a medium. (iii) Light travels faster than sound 2. Set up the apparatus as shown with the bell ringing.

Turn on the vacuum pump; as the air gets pumped out the sound gradually fades3.(i) Flash of lightning (ii) Light travels faster than sound 4. Echoes are produced when sound reflects off a surface.5.(i) Eye protection (ii) Ear protection must be worn to protect your ears.(iii) To prevent damage to hearing

Other Test Questions 1. How is sound produced?

2. Draw a labelled diagram of an apparatus used to show that sound is a form of energy.

3. Why is the moon sometimes referred to as “the silent planet”?

4. Draw a diagram and write a brief note to demonstrate that sound is caused by vibrations.

5. Draw a diagram and write a brief note to demonstrate that sound cannot travel through a vacuum.

6. What is ultrasound?

7. What is the speed of sound in air?

8. How are echoes produced?

9. Give two differences between sound and light waves.

10. Give two applications of reflected sound.

11. In a thunder and lightning storm, why do we see the lightning before we hear the thunder?

12. If the time-lag between seeing lightning and hearing thunder is 5 seconds, how far away is the storm?

13. When a girl was a certain distance from a high cliff she shouted loudly. One and a half seconds later the echo returned from the cliff. How far was the girl from the cliff? (take the speed of sound to be 340 m/s).

14. A guitar string is plucked. The sound is heard. It seems simple, but there are a few stages in between. Can you put the following stages in the correct order?

vibrating eardrum, brain, vibrating source, vibrating air, nerve

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Physics: 10. LightPlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOP33 Understand that light is a form of energy and that it can be converted to other forms

OP34 Show that light travels in straight lines and explain how shadows are formed.

OP35 Understand that luminous objects are a source of light while non-luminous objects are seen as a result of light reflected from them.

OP36 Recall that white light is made up of different colours which can be separated by dispersion.

OP37 Produce a spectrum of white light using appropriate apparatus, and list the colours of the spectrum.

OP38 Investigate the reflection of light by plane mirrors, and illustrate this using ray diagrams. Demonstrate and explain the operation of a simple periscope.

OP39 (all higher level) Show the refraction of light as it passes from: air to glass, air to water, glass to air, water to air.Show refraction of light through a lens.Demonstrate the operation of a magnifying glass.

Student Notes

To show that light is a form of energy you must be able to show that it can do work (because energy is the ability to do work). Work is done when an object is being moved. So we need to show that light can move something.DemonstrationUs a solar panel connected to a motor; when light shines on the solar panel the light energy gets converted to electrical energy and this then gets converted to kinetic energy in the motor (which turns).

DemonstrationNotice that you can only see light from the lamp when the holes in the card are lined up (use a piece of cord to line them up).

Shadows are formed when light coming from a source is blocked. The shadow is then similar in outline to the object blocking the light.Demonstration:Place your fingers between a candle and a screen and notice that as you bring your finger closer to the candle more light gets blocked out and the shadow gets bigger.

We can see objects because some of the light which leaves the objects hits our eyes.

Luminous objects are a source of light while non-luminous objects are seen as a result of light reflected from them.Examples of luminous objects: the sun, a light-bulb, a candle.Examples of non-luminous objects: everything else (not emitting their own light)

To investigate the reflection of light by plane mirrorsDemonstrationUse a ray box to shine a ray of light off a mirror.

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Light is a form of energy and it can be converted to other forms

Light travels in straight lines

How shadows are formed

Reflection is the bouncing of light from a surface

Notice that it reflects back out at the same angle as it goes in.

How a periscope worksSome of the light coming from the card hits the first mirror, then gets reflected from this onto the second mirror where it gets reflected again and travels out to the eye of the observer.

Dispersion and RefractionWhite light is made up of different colours which can be separated by dispersion

Make up a mnemonic to help yourself remember them e.g. Rover Often Yelps Grating Burglars Into Vegetables ??

To produce a spectrum of white lightUse a light bulb, a prism and a screen. Turn the prism slowly until a spectrum is formed on the screen.Note that red gets bent the least and violet gets bent the most, so X is red and Y is violet.

To demonstrate refractionShine a ray of light into a glass block and notice that it bends on the way in and also on the way out.

Show refraction of light through a lensA lens is a curved piece of glass used to bend (refract) light inwards or outwards.

To demonstrate the operation of a magnifying glassA magnifying glass refracts light to give a magnified image of the object.

Applications of refractionYou only need to know a couple of these:Lenses, spectacles, magnifying glass, microscope, binoculars, telescopes, camera lenses, prisms, projectors, endoscope, periscope etc.

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Refraction is the bending of light as it passes from one medium to another

Dispersion is the breaking up of white light into its individual colours (called a spectrum)

The colours of the spectrum are Red, Orange, Yellow, Green, Blue, Indigo and Violet.


The diagram shows a ray of light striking a plane mirror.(i) Complete the path taken by the ray in the diagram.(ii) Name the property of light shown.

2. [2008]The photograph shows a wader i.e. a bird that feeds in shallow water.

(i) Is the image of the bird produced by reflection or by refraction? (ii) Give a reason for your answer.

3. [2006 OL] The equipment shown in the diagram was set up and used in an experiment on light.

(i) What would the eye on the right see if the middle card was moved slightly?(ii) What does this experiment tell us about light?

4. [2007 OL] Describe, with the help of a labelled diagram, how you could carry out an experiment to show that light travels in straight lines.Use the following headings: Equipment: Result: Labelled diagram

5. [2007 OL] The diagram shows a ray of light shining onto a plane mirror in a periscope.Complete the path taken by the ray in the diagram.

6. [2006]A pupil made a simple periscope using two plane (flat) mirrors.The mirrors were arranged as shown in the diagram. The pupil looked through the periscope at the word ‘Science’ written on a card pinned to the laboratory wall.Did the pupil see first image or the second image when she looked through the periscope? Give a reason for your answer.

7. [2006]Why is the word Ambulance painted in reverse on the front of many ambulances?

8. [2008 OL]The equipment shown in the diagram was set up and used in an experiment on light.

(i) Name the piece of equipment labelled A.(ii) Name the colour labelled B.

9. [2008]The photograph shows narrow beams of light (rays) passing through a lens-shaped piece of transparent material. Parallel rays of light enter the material from the left and when they leave the material they converge and pass through a common point, before moving apart.Give a use for a lens having this effect on light.

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10. [2008]The diagram shows a ray of white light entering a triangular glass prism. The light passes through the prism and emerges as a band of coloured light.What does this experiment show about the composition of white light?

(i) What is this separation of white light into different colours called? (ii) What name is given to the band of coloured light produced?(iii) State the colour of the light labelled X and the colour of the light labelled Y at

the extreme ends of the band of light illustrated in the diagram.

11. [2008 OL]The picture shows a flash of lightning.

(i) Which is detected first, the flash of lightning or the clap of thunder?(ii) What does this tell us about the speed of light?

12. [2007]Thunder and lightning occur during electric storms.Explain why we see the lightning before we hear the thunder.

13. [2006][2007]What is refraction of light?

14. [2007]Give an everyday example of an effect caused by refraction.

15. [2007]Name another way in which the direction of a light ray can be changed apart from refraction.

16. [2007]Give an application of this bending of light.

17. [2007]A glass block like the one shown in the diagram was used in an experiment in which a narrow beam (ray) of light was shone through it. The light passed from air to glass, on entry, and glass to air, on exit.The path of this light ray is shown in the second diagram.The light ray from A bends both on entering and on leaving the glass block.Pick, from ‘rays’ P, Q, R or S the path taken by the light ray leaving the glass.

40

Exam Solutions

1. The reflected ray should be going out at the same angle as the light ray is going in.Reflection

2. ReflectionThe water surface acts like a mirror

3. Nothing / card / no light Light travels in straight lines

4. Equipment: Three pieces of card with holes in centre Procedure: Set up cards with holes in straight line Place lit lamp at one end / look through to lamp at other end Result: Light travels straight through / light can be seen / move the card and light cannot be seen

5. The ray goes down and then out.6. The pupil would see the first image because the word was reflected twice.7. Because mirrors invert the image therefore when drivers look in their mirrors they see the word ‘Ambulance’ as it

would normally appear.8. A: Prism, B: Green 9. Magnifying glass/ microscope/ camera/ projector/ binoculars/ telescope/ spectacles (glasses)/ start a fire/ focus

infra red (IR) (heat)/spotlight… 10.(i) White light is a mixture of different colours.(ii) Dispersion(iii) A spectrum(iv) X is red , Y is violet/ purple11.(i) The flash of lightning (ii) Light is travels faster than sound 12. Light moves faster than sound.13. Refraction is the bending of light as it passes from one medium to another.14. Rod partly in water appears bent/ water appears to be shallower than it really is/ formation of an image by a lens/

rainbow/ mirage… 15. Reflection 16. Lenses/ spectacles/ magnifying glass/ microscope/ binoculars/ telescopes/ camera lenses/ prisms/ projectors/

endoscope/ periscope/…17. R

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General Questions

1. Why is lightning seen before the thunder is heard?

2. Describe briefly how you would show the conversion of light energy to electrical energy to kinetic energy.

3. Draw a diagram and write a brief note to demonstrate that light is a form of energy.

4. What is meant by the reflection of light?

5. What is meant by a luminous object?

6. Give an example of a luminous object.

7. Give two observations that suggest that light travels in straight lines.

8. How would you demonstrate that light travels in straight lines?

9. Show using a diagram how a periscope works. Include rays of light and make sure to put arrows on all rays. It might help to turn this page sideways for the diagram.

10. Explain, using a diagram, how a shadow of a person is formed on a sunny day.

11. Describe how you would investigate the reflection of light from a plane mirror?What results would you expect to notice?

12. Draw a diagram to show how light is reflected from a plane mirror.

13. Describe with the aid of diagram how a periscope works.

14. What is refraction?

15. What is the name given to the change in direction of light as it enters a prism?

16. Describe, with the aid of a diagram, an experiment to show the refraction of light as it passes through a lens.

17. Draw diagrams to show how(i) a Concave Lens, and (ii) a Convex Lens works

18. Explain, with the aid of a diagram, how a magnifying glass works.

19. What is the name given to the spreading out of sunlight into a band of colour?

20. Describe how you would investigate the dispersion of white light through a prism.

21. What is the name given to the band of colour itself?

22. How would you demonstrate dispersion?

Higher Order QuestionsWhy do rainbows often appear after a heavy shower of rain?

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Physics: 11. HeatPlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

Syllabus OP22 Understand that heat is a form of energy and that it can be converted into other forms of energy

OP23 Investigate and describe the expansion of solids, liquids and gases when heated, and contraction when cooled

OP24 Demonstrate the expansion of water on freezing

OP25 Measure the temperature of various solids and liquids at, above and below room temperature; determine the melting point of ice and the boiling point of water

OP26 Investigate the effect of pressure on the boiling point of water

OP27 Explain the difference between heat and temperature

OP28 Carry out experiments that involve changes of state fromi. solid to liquid and liquid to solidii. liquid to gas and gas to liquid

OP29 Plot a cooling curve and explain the shape of the curve in terms of latent heat

OP30 Understand that all hot bodies radiate heat

OP31 Carry out simple experiments to show the transfer of heat energy by conduction, convection and radiation; investigate conduction and convection in water

OP32 Identify good and bad conductors of heat and compare insulating ability of different materials.

Student Notes

To show that heat is a form of energy you must be able to show that it can do work (because energy is the ability to do work). Work is done when an object is being moved. So we need to show that heat can move something.DemonstrationAlcohol in a thermometer moves up the glass when heat is applied.

Solids expand when heated and contract when cooledDemonstration1. Heat the brass ball.2. Note that he ball fits through the ring when the ball is cold but not when hot.

Liquids expand when heated and contract when cooledDemonstration1. Insert a glass tube into a beaker of water (use dye to make it visible).2. Note that the water rises up the tube as it gets heated and drops back down as it cools.

Gases expand when heated and contract when cooledDemonstration1. Gently heat the flask of air.2. Note that bubbles come out of the tube when the flask is heated and as it cools

water from the trough rises back up the tube because of the partial vacuum which has formed.

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Solids, liquids and gases expand when heated, and contract when cooled

Heat is a form of energy and it can be converted into other forms of energy

Temperature is a measure of the hotness or coldness of an

The anomaly (strangeness) of waterWater is an exception to almost all other substances in that when it drops below 4 0C the water actually expands when cooling rather than contracting.The explanation for this is a little complicated (it has to do with the arrangement of water molecules, but you don’t need to know it for exam purposes).Demonstration1. Fill a glass bottle with water and place it in a plastic bag in a freezer.2. When you take it out the following day the bottle will be broken because the water has expanded on freezing.

(The purpose of the bag was to ensure that all the pieces of glass get taken out).This is why water pipes sometimes burst in winter causing flooding in a home.

The effect of pressure on the boiling point of water

Demonstration1. Suck up water which is at about 80 0C into the syringe so that the syringe is about one-quarter full. 2. Cover the open end (watch out- it’s hot!) and pull back the handle to create a partial vacuum.3. The water begins to boil!4. Explanation: the air acts like a blanket which presses down on the water and makes it difficult for the water

molecules to leave the liquid and become part of the air. 5. Higher pressure therefore results in a higher boiling point (the molecules need to have more energy/ move more

rapidly to make the transition).

Changes of state, the cooling curve and latent heat

1. Heat a boiling tube of wax to a high temperature and as it cools note the temperature.

2. Plot a graph of temperature against time.3. Note that the temperature decreased at a steady rate until (in this case) it

reached 80 0C.4. This is when the wax began to change state from a liquid to a solid.5. It remains at this temperature until all the wax has solidified (in this case

it took 5 minutes) and after that it began to drop in temperature again as the solid wax cooled down.

ExplanationAs the wax changes state from a liquid to a solid it gives out heat without cooling down. This heat is called latent heat because latent means ‘hidden’ and in this case it is not obvious where the heat is coming from.Latent heat is therefore the heat taken in or given out when a substance is changing state (without changing temperature).

Heat Transfer: Conduction, Convection and RadiationHeat can be transferred in three different ways - conduction, convection and radiation

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Reduced pressure decreases the boiling point of water

Conduction is the method by which heat travels from particle to particle through a solid

Convection is the transfer of heat through a liquid or gas when the particles move and carry the heat with them

Radiation is the transfer of heat from a hot object without the need for a medium

All objects radiate heat, but not all substances conduct or convect heat

Conduction Convection RadiationSolids Yes No Yes

Liquids No Yes YesGases No Yes Yes

ConductionTo compare the ability of different metals to conduct heat1. Use the apparatus shown which consists of a piece of timber with four different strips of metal.2. Place some candle wax at the end of each metal and stand a match in the wax at the end.3. Light the Bunsen (or candle) under the middle and note the order in which the matches fall.

The match which falls first was standing in the best conductor.

To show that water is a poor conductor of heat1. Half fill a boiling tube with water and use piece of metal gauze to hold down the ice.2. Holding the boiling tube at an angle with a tongs, heat it at the top using the Bunsen burner for a

short period of time.Result: the water at the top boils which the ice at t he bottom stays frozen.

ConvectionTo demonstrate convection currents in water1. Use the apparatus shown and drop in some copper sulphate or potassium permanganate to act as a dye.2. Place the Bunsen under one of the corners and note the movement of the water around the apparatus.

To demonstrate convection currents in airCut tissue paper into narrow strips; tie the strips together at one end using the piece of thread and hang them from a retort stand as shown over a hot-plate.Result: the tissue paper will begin to move as a result of the convection current generated by the hot-plate.

RadiationShiny substances are better radiators of heat than dark substancesDemonstration1. Take two identical metal containers and paint one with one black and the other silver.2. Fill both with hot water.3. Note which container cools more quickly than the other.4. The silver container cooled more quickly because it is a better radiator of heat.

Conductors and Insulators

To compare the insulating ability of different materialsDemonstration1. Take two identical containers and wrap one in cotton wool.2. Fill both with hot water.3. Note which container cools more quickly than the other.4. The container which cooled more slowly had better insulating material.

Note: There are no maths problems in this chapter.

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A conductor is a substance which allows heat to flow through it easily

An insulator is a substance which does not allow heat to flow through it easily

radiator


Define temperature and give a unit used to express temperature

2. [2008]Give two differences between heat and temperature.

3. [2007 OL] The apparatus drawn consists of a ball and ring.When the ball and the ring are cold the ball just fits through the ring.When the ball is heated the ball does not pass through the cold ring.

(i) What conclusion would you draw from this experiment? (ii) What would you expect to happen if the ball was cooled down again?

4. [2007]The diagram shows a “ball and ring” apparatus.When the ball and ring are both cold the ball just passes through the ring.How would you use this apparatus to show

(i) the expansion of a solid on heating(ii) the contraction of a solid on cooling?

5. [2009 OL]Describe, with the help of a labelled diagram, how you could carry out an experiment to show that metals expand when heated.Use the following headings: Labelled diagram, Equipment, Procedure, Result.

6. [2008 OL]The diagram shows a round-bottomed flask full of coloured water.

(i) What would you expect to notice if the flask is heated gently? (ii) Give a reason why this should happen.(iii) Why is coloured water used during this investigation?

7. [2007 OL] In an investigation to see the effect heating had on gases, a student heated a round-bottomed flask containing air using a hairdryer as shown in the diagram.

(i) What would you expect the student to have seen when the flask was heated?

(ii) What conclusion can you draw from this investigation?

8. [2006 OL] Heat may be transferred from hot to cold places by the three methods listed on the right.Choose the method of heat transfer that occurs in each of the following.

(i) The boiling of water in a kettle. ___________________________(ii) The heating of the Earth by the Sun. ___________________________

9. [2006]Describe an experiment to show the expansion of water when it freezes.You may include a labelled diagram if you wish.

10. [2009]The boiling point of water can be determined using the apparatus shown in the diagram.

(i) Why are boiling (anti-bumping) chips added to the water? (ii) At what temperature does water boil, at standard (normal) atmospheric pressure? (iii) What effect does the raising of pressure have on the boiling point of water? (iv) What effect does the lowering of pressure have on the boiling point of water?

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CONDUCTIONCONVECTIONRADIATION

Conduction, Convection and Radiation11. [2007 OL]

Heat is transferred in different ways.In each case use a word from the list on the right to correctly complete each sentence below.

(i) Heat travels through solids by ___________________.(ii) Heat travels through liquids and gases by ___________________.(iii) Heat travels from the Sun to the Earth by ___________________.

12. [2006]Name the mode of heat transfer from the hot liquid, through the spoon, to the hand.

13. [2009]Copper, aluminium and iron rods are set-up as shown in the diagram. A metal ball is attached by wax to the end of each rod. Hot water is poured into the beaker. The ball falls from the copper rod first. What conclusion can be drawn from this observation?

14. [2007](i) What does the experiment shown in the diagram tell us about the transfer of heat energy in

water?(ii) If you wanted to warm all of the water why would the bottom of the test tube be the best

place to heat with the Bunsen flame?

15. [2006]Heat moves in liquids by convection. Give one difference between convection and conduction.

16. [2009]The photograph shows a solar panel being installed. Water passing through the panel is heated by the sun.

(i) How does heat from the sun travel, through the vacuum of space, to the earth? (ii) Give one advantage or one disadvantage of fitting solar panels to your home?

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ConductionConvectionRadiation

Latent Heat17. [2008]

A pupil heated some lauric acid, which is a solid at room temperature, until it turned into a liquid. The lauric acid was then allowed to cool at a uniform rate. The temperature of the lauric acid was taken every minute.The data from this experiment is given in the table.

(i) Draw a graph, using this data, of temperature against time (x-axis) in the grid provided below.

(ii) Explain the shape of the graph that you obtain.

(iii) Use the graph to estimate the melting point of lauric acid.

18. [2006]The graph is a cooling curve. The substance used in this experiment was naphthalene. Naphthalene has a melting point of 80 0C.The rate of heat loss was constant throughout the experiment.

(i) What is happening to the naphthalene between points A and B on the graph?

(ii) What is the heat loss, between points A and B, on the curve called?

19. [2009 OL]The diagram shows two metal cans equal in size and filled with the same amount of water at 100 °C. Can A is wrapped in cotton wool and can B has no wrapping.

(i) After 15 minutes, which can, A or B, would you expect to have the higher temperature?

(ii) Give a reason for your answer.

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Temperature (0C) 75 64 54 43 43 43 43 43 32 22 10Time (minutes) 0 1 2 3 4 5 6 7 8 9 10

Exam Solutions1. Temperature is a measure of the hotness of an object.

The unit of temperature is degrees Celsius (0C).2. Heat is a form of energy (and temperature isn’t).

Temperature is a measure of the hotness of an object (and temperature isn’t).3. (i) Solids (metals) expand (when heated) / ball expands (when heated) (ii) It would fit through the ring / contracts / get smaller4.(i) Heat the ball, it does not pass through the ring.(ii) Let the ball cool, it now passes through the ring again.5. Ball and ring apparatus as shown.

Ball fits through ring when both are at room temperature.Heat the ball over a Bunsen burner for one minute. Result: the ball will no longer fit through the ring.

6.(i) Water rises up the tube (ii) Water (liquid) expands (when heated) (iii) Easier to see 7. (i) Bubbles of air coming from the mouth of the flask into water trough(ii) Air (gas) expands when heated 8. (i) Convection (ii) Radiation 9. Fill a bottle with water

Put the bottle in a freezer The bottle bursts after a few hours.

10.(i) Chips help to ensure that all the water boils at the same temperature{I know – not on the syllabus so shouldn’t

have appeared!}(ii) 1000 C(iii) It raises the boiling point(iv) It lowers the boiling point

Conduction, Convection and Radiation11. (i) Conduction(ii) Convection (iii) Radiation 12. Conduction 13. Copper is the best conductor14.(i) Water is a poor conductor of heat (ii) Because hot water rises (note that ‘heat rises’ alone gets no marks)15. Convection: particles of liquid move carrying the heat with them.

Conduction: heat is transferred from one particle to another without any overall movement of the particles themselves.

16.(i) It travels by radiation.(ii) Advantage: to reduce fuel bills, reduce CO2 emissions, it is renewable.

Disadvantage: expensive to set up, less heat is absorbed in winter or on cloudy days.

Latent Heat17.(i) See graph(ii) Initially the temperature of the liquid falls until it reaches 43 0C.

Here it changes state from a liquid to a solid.Then the solid cools down.

(iii) 43 0C

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18. (i) It is changing from a liquid to a solid (ii) Latent heat of fusion

19.(i) Can A will have a higher temperature after 15 minutes. (ii) Because it is insulated so it loses heat more slowly.

Heat Questions1. Draw a labelled diagram of an apparatus used to demonstrate convection in a liquid.2. Draw a labelled diagram of the apparatus used to compare the conductivity of different metals. How does it work?3. Give two uses of a bimetallic strip.4. Draw a labelled diagram of the apparatus you would use to show that water is a poor conductor of heat.5. How would you demonstrate that solids expand when heated and contract when cooled? Include a fully labelled

diagram.6. How would you demonstrate that liquids expand when heated and contract when cooled? Include a fully labelled

diagram.7. How would you demonstrate that gas expands when heated and contract when cooled? Include a fully labelled

diagram.8. Why is water not a suitable liquid for use in thermometers?9. Define conduction.10. Define convection.11. A student filled a boiling tube with water and placed an ice-cube at the bottom by keeping metal weight on top of

it. The student then heated the top of the boiling tube until the water was boiling at the top. (i) What was the student trying to investigate?(ii) Why did he put a weight on the cube of ice?(iii) Why was it important that the weight was made of metal?(iv) What did the student notice?12. Fill in the table with the words convection, conduction, or radiation where appropriate

Object Method of Heat TransferA spoon

A saucepan of waterSpace

13. Why is the heating element of a kettle placed near the bottom?14. What is the main way in which heat is transferred when the water in an electric kettle is heated?15. What is the main way in which heat is transferred when the Sun heats the Earth?16. What property of oven gloves allow a baker to pick up hot bread?17. Why do metals expand when heated?18. What is meant by the term ‘the anomaly of water’?19. Sublimation occurs when a ________ changes directly to a ________ when heated.20. What is meant by the term ‘latent heat’?21. Draw a diagram of a cooling curve for wax and indicate on it all the various states of matter.

Higher Order Questions22. When stepping out of bed on a cold morning, why does it feel colder if your feet touch say, a marble floor rather

than a floor with carpet even though both are at the same temperature?23. How does perspiration (sweating) help to keep us cool?24. Many Arabs wear dark clothing in warm weather, even though dark clothes are better at absorbing heat than white

clothes. Any idea why?25. Heat can be transferred by conduction, convection or radiation. A thermos flask tries to keep hot liquids hot by

preventing heat loss. Any idea how it minimises each of these three methods of heat transfer? 26. What is the effect of increased pressure on the boiling point of water27. Why does increased pressure affect the boiling point of water?

Can you think of an application of this (a device which is built on this principle?Can you think of anyone who might be affected by this?

For more higher order questions see http://nse.ie/JSSS_CD/Hubpages_55/3B1_Heat/3B1_OP23_Teacher.pdf

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http://nse.ie/JSSS_CD/Hubpages_55/3B1_Heat/3B1_OP23_Teacher.pdf

Test questionWhy are ice cubes much better at cooling a drink that the equal amount of iced water?Why is a scald from steam much more serious that a burn from boiling water?Why do hurricanes pick up energy when they pass over oceans?

Hurricanes pick up energy while travelling over the ocean.Water evaporates and in doing so picks up heat energy when going from a liquid to a gas.Now later on when it condenses from a gas to a liquid it gives out this heat in the form of molecular energy to nearby molecules which presumably heats them up.

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Physics: 12. MagnetismPlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOP45 Carry out simple experiments to show attraction and repulsion between magnets, and test a variety of

materials for magnetism

OP46 Plot the magnetic field of a bar magnet

OP47 Demonstrate that the Earth has a magnetic field, and locate North and South.

Student NotesTo show attraction and repulsion between magnets

1. Hang a magnet as shown (the dark half represents the north-pole).2. Bring another magnet up close to it.3. Notice that if you bring up a north-pole it repels the north of the first magnet, but if you bring up the

south-pole end it attracts the north-pole of the first magnet.Conclusion:Similar poles repel, opposite poles attract

To test a variety of materials for magnetismTo test a material for magnetism bring a magnet up to it and see if the material becomes attracted to the magnet.

To plot the magnetic field of a bar magnet

Equipment: Magnet, sheet of paper, compasses Procedure: Place the plotting compass beside the magnet and mark the position of the north end. Move the position of the compass and repeat a number of times on both sides of the magnet. Join the dots. Result: a pattern is formed on the paper representing the magnetic field of the magnet.

The lines joining the North and South poles are called magnetic field lines; they are most concentrated at the poles.Magnetic field lines are drawn going from north to south.

To demonstrate that the Earth has a magnetic field, and locate North and South.

When we allow magnets to hang free, they come to rest with one end facing north and the other facing south.We therefore label the north-facing end ‘the North Pole’, and the south-facing end ‘the South-Pole’. ‘pole’ means ‘end’.

Uses of magnetsFridge magnets, in motors, in speakers

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The diagram shows a magnet freely suspended from a wooden stand.Complete the statements below using the correct word from the list on the right in each case.

(i) When the north pole of another magnet is brought close to the north pole of the hanging magnet they will ___________ each other.

(ii) When the south pole of another magnet is brought close to the north pole of the hanging magnet they would _____________ each other.

2. [2006 OL][2009 OL]The diagram shows a bar magnet.

(i) Draw the pattern made if iron filings or plotting compasses were placed around the bar magnet.(ii) Give one use of a magnet.

3. [2007]The diagram shows the outline of a bar magnet.

(i) Draw two magnetic field lines one on each side of the bar magnet.(ii) What are the parts labelled N and S in the diagram called?

4. [2008 OL]Describe, with the help of a labelled diagram, how you could carry out an experiment to plot the magnetic field of a bar magnet.Use the following headings: Labelled diagram, Equipment, Procedure, Result.

Exam Solutions1. (i) Repel (ii) Attract 2.(i) See diagram (one above and one below) (ii) Fridge magnets / in motors / in speakers 3.(i) See diagram (note that you must include the arrows going from N to S)(ii) Poles4. Equipment: Magnet, sheet of paper, compasses

Procedure: Place the plotting compass beside the magnet and mark the position of the north end. Move the position of the compass and repeat a number of times on both sides of the magnet. Join the dots and include arrows indicating that the field lines are going from North to South.

Result: a pattern is formed on the paper representing the magnetic field of the magnet.


1. Complete the following in your answerbook: Like poles ___________, unlike poles ___________

2. Describe an experiment to plot the magnetic field around a bar magnet and illustrate the magnetic field.

3. List two uses of magnets.

4. What is a compass and how does it work?

5. What is a space around a magnet called?

6. Draw a diagram of a bar magnet and sketch some magnetic field lines around it.

7. Show by means of arrows the directions of the lines of force.54

RepelAttract

Physics: 13. Static ElectricityPlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOP48 Use simple materials to generate static electricity; demonstrate the force between charged objects and the

effects of earthing.

Student Notes

When one object is rubbed against another, charges (electrons) often get transferred from one object to the other.Remember that electrons have a negative charge.An object becomes positively charged if it loses electrons, and negatively charged if it gains electrons.

Demonstration: using simple materials to generate static electricityOption 1: Rub a biro or a balloon with a cloth to charge it and then use it to attract pieces of paper.Option 2: A charged balloon can attract an empty coke can which is lying on a table.Conclusion: Neutral objects are attracted to charged objects

To demonstrate the force between charged objects Charge a plastic rod by rubbing it with a cloth and then hang it from a retort stand.Rub another rod with the same cloth (so that it will have the same charge) and bring it up to the first rod.The first rod will be repelled by the second rod because they both have the same charge and similar charges repel.

Next bring up a different type of charged rod (which has an opposite charge and notice that it attracts the first rod because they both have opposite charges and opposite charges attract.

EarthingEarthing means connecting a charged object to the earth by means of a conductor, so that most of the charge which was on the object flows to the earth.

If a rod is charged then all the charges on the rod are repelled from each other and will try to escape from the material if they can. If the material is an insulator like plastic then the charges are not able to move and so remain on the material.However if you touch the material with your fingers then the points of contact become ‘earthed’ because the charges get transferred to earth via your body. When an object loses charge in this manner we say it gets ‘earthed’.

Similarly the charges can transfer into the air if there is a lot of moisture in the air because water is a conductor.

Useful effects of static electricity1. Removing soot from chimneys2. Spray-painting

Nuisance effects of static electricity1. Television screens attracting dust2. Lightning

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A conductor is a substance that allows charge to flow through it easily (metals are conductors)

An insulator is a substance that does not allow charge to flow through it (plastics are insulators)

Similar charges repel; opposite charges attract


A student set up the circuit drawn on the right to investigate different materials to see which were electrical conductors and which were electrical insulators.

(i) What would you expect to observe when an electrical conductor is connected between the contact points A and B? Give a reason for your answer.

(ii) What would you expect to observe when an electrical insulator is connected between the contact points A and B? Give a reason for your answer.

2. [2008]Two rods A and B, made from different plastics, were given the static electrical charges shown in the diagram.How could you have charged the rods as shown?

3. [2008]Describe with the help of a labelled diagram how the force between the two charged rods A and B could be investigated.What result would you expect from this investigation?

4. [2008]In dry weather you can sometimes get an electric shock from a supermarket trolley. This is caused by the build-up of static electricity on the trolley.Explain clearly why this only happens in dry weather.

5. [2009]A plastic pen when rubbed with a dry cloth can attract small pieces of paper which ‘stick’ to it.

(i) Why does this happen?(ii) Explain why the pieces of paper fall from the pen after some time.

6. [2006 OL] The picture shows a flash of lightning.

(i) What type of energy generates lightning?(ii) The flash of lightning is seen before the thunder is heard.

What does this tell us about the speed of light?

Exam Solutions

1.(i) The bulb lights because there is a complete (closed) circuit.(ii) The bulb doesn’t light because the circuit is still broken (the material doesn’t conduct)’2. By rubbing them with a cloth3. Suspend the rods as shown

Bring the rods close togetherResult: The rods attract each otherORBalance one rod on a clock glass and bring the other rod up close to it.Result: The rod balanced on the glass rotates towards the hand-held rod.

4. In wet weather moisture allows electric charge to escape.5.(i) Because the pen has charge (ii) The pen loses its charge6. (i) Static electricity (ii) Light travels faster than sound

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1. What is the difference between a conductor and an insulator?

2. Write out the following sentence, filling in the missing words: similarly-charged objects ______________ while oppositely-charged objects ______________.

3. Describe briefly how you would investigate the relationship between two similarly charged objects.

4. Sometimes when you touch a metal object (like a shopping trolley) you can get a small shock. Why is this more likely to happen on a dry day than on a wet day?

5. Give one example of when static electricity is useful and one example of when static electricity can be a nuisance (apart from getting a shock)?

6. When a Perspex rod is rubbed with a cloth it becomes positively charged. Explain in terms of electron transfer how this occurs.

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Physics: 14. Current ElectricityPlease remember to photocopy 4 pages onto one sheet by going A3→A4 and using back to back on the photocopier

SyllabusOP49 Test electrical conduction in a variety of materials, and classify each material as a conductor or insulator

OP50 Set up a simple electric circuit, use appropriate instruments to measure current, potential difference (voltage) and resistance, and establish the relationship between them

OP51 Demonstrate simple series and parallel circuits containing a switch and two bulbs

OP52 Perform simple calculations based on the relationship between current, potential difference (voltage), and resistance

OP53 Describe the heating effect, the chemical effect, and the magnetic effect of an electric current, and identify everyday applications of these, including the action of a fuse

OP54 Distinguish between direct and alternating current; recall that the voltage of the mains supply is 230 volts a.c.

OP55 Recall that the unit of electrical energy used by electricity supply companies is the kilowatt-hour, and calculate the cost of using common electrical appliances, based on their power rating

OP56 Describe how to wire a plug correctly, and explain the safety role of a fuse or circuit breaker in domestic electrical circuits.

Student NotesConductors and InsulatorsRemember our definitions of conductors and insulators from the chapter on Static Electricity:A conductor is a substance that allows charge to flow through it easily (metals are conductors).An insulator is a substance that does not allow charge to flow through it (plastics are insulators).

Experiment: Identify materials as conductors or insulators1. Set up the circuit as shown.

2. Place various different materials between points X and Y in the circuit and turn on the switch.

3. If the bulb lights then the material is a conductor and if it doesn’t then the material is an insulator.

ResistorsA resistor is used to reduce the flow of current in a circuit.

A series circuit This is where the two bulbs are connected one after the other.All the current coming from the battery goes through both bulbs.Advantage: Uses less electricity than if the bulbs are connected in parallel.Disadvantage: If one bulb blows the circuit is broken and so no current flows, e.g. lights in a Christmas tree.

A parallel circuitThe current coming from the battery splits up and some goes through each bulb.Advantage: If one bulb blows there will still be a complete circuit through the other bulb so it will remain lit.Light bulbs in a house are generally connected in parallel for this reason.Disadvantage: It uses more electricity than if connected in series.

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Label Circuit component

A Switch

B Power supply

C Resistor

D Bulb

Current, voltage and resistance

1. Current

The unit of current is the amp (the symbol for the amp is A). The symbol for current is I. Current is measured with an ammeter or multimeter.

For current to flow we need two things:1. There has to be a complete circuit.2. There has to be a source of potential difference (power supplies and batteries both act as a source of potential difference).

2. Potential difference (commonly called ‘voltage’)Current will flow between two points if there is a potential difference between the two points.This is a bit like saying that water will flow between two points if there is a height difference between the two points.

Another way of thinking about potential difference is that it provides the ‘push’ to move the electrons around a circuit. The unit of potential difference is the volt (the symbol for the volt is V) The symbol for potential difference is V. Potential difference is measured with a voltmeter or multimeter.

3. Resistance

The unit of resistance is the ohm (the symbol for the ohm is Ω). The symbol for resistance is R. Resistance is measured with an ohmmeter or mulitmeter.

Summary

Relationship between current, potential difference and resistance

Experiment: To establish the relationship between potential difference and current1. Set up the circuit as shown and note the current (I) and potential difference (V)2. Adjust the variable resistor (rheostat) to get a new set of values.3. Repeat about 6 times and then plot a graph of potential difference

against current.4. The fact that we get a straight line shows that the potential

difference is proportional to the current (this means that if we double the potential difference, the current will double also).

5. Note that the slope of the graph corresponds to the resistance of the component.

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Quantity Symbol Unit Symbol Measured with Symbol

Current I Amps A Ammeter

Potential difference V Volts V Voltmeter

Resistance R Ohms Ω Ohmmeter

Current is a flow of charge (the charge is usually electrons)

V = RI

Resistance opposes the movement of electrons around a circuit

In an electric circuit current flows from the positive end of the battery to the negative endThe positive end is represented with a long solid line, and the negative end is represented with a short solid line

Maths problemsCalculate the resistance of a resistor when 20 V produces a current of 4 A.AnswerR = V÷I = 20 ÷ 4 = 5 Ohms

Effects of an electric current

There are three effects of an electric current; a heating effect, a magnetic effect and a chemical effect

Effect Demonstration Everyday applicationHeating Effect An electric current will cause a light-bulb to heat

up and emit lightElectric kettle, electric fire etc.

Magnetic Effect

An electric current will deflect a magnetic compass

Electromagnets

Chemical Effect

Electrolysis occurs when an electric current splits water into hydrogen and oxygen

Electroplating

Heating Effect Magnetic Effect Chemical Effect

Alternating Current (a.c.) and Direct Current (d.c.)

Mains ElectricityElectricity which comes through the sockets in your house is referred to as ‘mains’ electricity’.It changes direction 50 times per second and so is called alternating current (a.c.).

Look at the back of your electrical appliance and it will state this voltage and also the power.

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Direct current is current which flows in one direction only; alternating current is current which constantly changes direction.

‘Mains’ voltage is 230 volts

Fuses

The 3-pin plug

Cost of electricity - the kilowatt-hour

The ESB charges for electricity at a rate of 11 cent per kW h.A hair-drier of power rating 1.5 kW is used for 20 minutes each day.(i) How many units of electricity are used?(ii) What is the cost, in cent, of using the hair- drier for six days?Answer(i) Six days corresponds to 120 minutes or 2 hours.

The number of kWh = kW × hours = 1.5 × 2 = 3 kWh (ii) Cost = 3 kWh × 11 cent per kWh = 33 cent

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A fuse is a deliberate weak link in a circuit which will break (melt) if the current exceeds a preset value

The unit of electrical energy used by electricity supply companies is the kilowatt-hour

The number of kilowatt-hours equals the number of kilowatts multiplied by the number of hours

kWh = kW × hours

The neutral wire is blue. The earth wire is yellow or green. The live wire is brown or red. The fuse is on the live wire.

Exercises

Fill in the following table using the formula V = IR:

Fill in the following table:

Activity:Check appliances at home (e.g. hairdryers, lamps, heaters etc) to find the power rating and use this to fill in the table below.

The power rating of various appliancesYou don’t have to remember the numbers – just remember which machines use a lot of power and which use relatively little.In general, if an appliance has a motor in it (something which moves) then it will have a high power rating.

Appliance Power (in watts)Washing machine 2500

Microwave 1000

Light-bulb 40

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Potential Difference(V)

Current (I) Resistance(R)

10 52 200

120 30100 2

0.5 20120 10

Watts(W)

kilowatts(kW)

Hours(Hr)

kWhr Cost(12 cent per unit)

50 0.05 60 3 2420 5

1000 1 day500 10 minutes60 1 week

Appliance Power-rating (kW)

Average hrs used in a week

kWhr per week Cost over 1 week @ 9p per unit

(kWhr)


The diagram shows a simple electrical circuit.Complete the table below correctly matching each of the names of the components in the circuit with one of the labels A, B, C or D.

2. [2008 OL]You are given a piece of copper metal and a piece of timber. Which piece, metal or wood, should you connect between X and Y in order that the bulb would light when the switch is closed? Give a reason for your choice.

3. [2007 OL]A student set up the circuit shown to investigate the relationship between the potential difference (voltage), the current and the resistance of a wire conductor.Gaps are left in the diagram in the places where the ammeter and voltmeter should be placed. The symbols for these devices are given on the right.Complete the circuit inserting the symbols for the ammeter and the voltmeter in their correct positions.

4. [2007]The symbols for two electrical meters are given in the diagram. The symbol is for a meter that measures potential difference, often called ‘voltage’.What electrical quantity can be measured using the meter with the symbol ?

5. [2006]Components, e.g. bulbs, in electrical circuits can be connected in series or in parallel.It is noticed that, when one headlight fails (blows) in a car, the second remains lighting.

(i) State the way the headlights are connected and give a reason why this mode of connection is used.

(ii) All of the bulbs go out in an old set of Christmas tree lights, when one of bulbs fails (blows). In what way are the bulbs connected in this set of lights?

(iii) Explain why, when one bulb blows, they all go out.

6. [2006]Calculate the resistance of the filament of a car headlamp when 12 V produces a current of 5 A in it.In what unit is resistance measured?

7. [2007 OL]The student used the variable voltage supply to apply different voltages across the resistor. She measured the voltage across the resistor and the current passing through it several times. She collected the following data.

(i) Draw a graph of the voltage (y-axis) against the current (x-axis). (ii) What conclusion can you draw from the graph about the relationship

between the potential difference (voltage) and the current passing through the wire conductor?

8. [2007]Meters and are used in the circuit shown.Enter ‘A’ into the appropriate circle of one of the meter symbols in the circuit diagram so as to clearly identify its correct position.

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Label Circuit componentBulbPower supplyResistorSwitch

Voltage (V) 0 2 4 6 8Current (A) 0 0.5 1.0 1.5 2.0

9. [2007]A pupil used the circuit above to get a set of readings from both meters for different values and then plotted this data in the graph shown.Use this graph to calculate the resistance of resistor R shown in the diagram. Give the unit of resistance with your answer.

10. [2007]Give one application of the magnetic effect and one application of the chemical effect of electric current.

11. [2008]Distinguish between alternating and direct current.

12. [2008]What is the average voltage of domestic alternating current in Ireland?

13. [2006]Explain, clearly, the safety role of fuses in household electrical circuits.

14. [2007 OL]The diagram shows a three-pin plug with the back removed.

(i) In the table below write the letter X beside the name of the wire labelled X in the diagram.

(ii) Write the letter C beside the colour of the insulating on the wire labelled Y.

15. [2008 OL] The diagram shows a three-pin plug with the back removed.Answer the questions below using the table.

(i) In the table write the letter X opposite the name of the green and yellow wire.(ii) Write the letter Y opposite the name of the wire to which the fuse is connected.(iii) Write the letter Z opposite the function of the fuse in a plug.

16. [2006 OL] The diagram shows a three-pin plug with the back removed.

(i) What is the correct names for the cables labelled X and Y.(ii) Give one reason why the back covering (casing) of a plug is made from plastic.

17. [2008]Wiring a plug correctly is most important. Give the colour/s of any two of the plastic insulations on the wires labelled A, B and C.

18. [2008 0L](i) Write the letter C beside the unit of electric current.(ii) Write the letter E beside the unit of electricity used by the ESB for

costing.

19. [2006 OL] Appliances vary in the amount of electricity they use depending on their power rating.A tumble drier has a high power rating of 2.5 kW.

(i) Name another appliance found in the home that has a high power rating.(ii) Name an appliance found in the home that has a low power rating.

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VoltAmpereKilowatt Hour

20. [2007 OL]An electric cooker has four hot plates.The total power rating of the four hot plates is 7 kW.All four are used for a total of 2 hours each day.

(i) How many units of electricity (kWh) are used in 1 week?(ii) If electricity costs 11 cent per unit how much does this cost?21. [2006 OL]

The ESB charges for electricity at a rate of 12 cent per kW h.A tumble drier of power rating 2.5 kW is used for 2 hours each week for 4 weeks.

(i) How many units of electricity are used?(ii) What is the cost, in cent, of using the tumble drier?

Exam solutions1. A: Switch

B: Power supply C: Resistor D: Bulb / lamp

2. Metal, because metal is a conductor and wood is an insulator 3. Ammeter in series

Voltmeter in parallel (above the resistor).4. Current 5.(i) The headlights are connected in parallel because if one bulb blows the other remains on.(ii) They are connected in series.(iii) The circuit is broken.6. R = V/I = 12/5 = 2.4 Ohm/ Ω7.(i) The graph should result in a straight line through the origin.(ii)Potential difference is proportional to current.8. ‘A’ goes into the circle on the left-hand side.9. The resistance corresponds to the slope of the graph.

Pick two points from the graph and use the formula slope = y2 – y1 / x2 – x1

Slope = 12 Ω or 12 Ohms (accept 11.5 to 12.5)

10. Magnetic effect: electromagnets/ door bells/ central locking in cars/ speakers.Chemical effect: electroplating/ galvanising/ refining of copper.

11.Alternating current changes direction, direct current moves in the same (fixed) direction 12. 220-240 volts13. The fuse melts if the current is too high and this breaks the circuit.14.(i) X: Neutral (ii) C: (Y) Brown 15.(i) X: Earth(ii) Y: Live (iii) Z: Safety 16. (i) X: Earth Y: Live (ii) To prevent shock (electrocution) / safety / insulates17. A is blue/ B is green and yellow / C is brown 18. (i) C: Ampere (ii) E: Kilowatt hour 19.(i) Cooker / kettle / toaster / washing machine / dish washer etc(ii) Reading lamp / radio / television 20.(i) 7 × 2 × 7 = 98

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(ii) 98 × 11 = €10.78 21.(i) 2.5 × 2 × 4 = 20 kWh (ii) 20 × 12 = 240 cent

Other Test Questions1. Why is electricity a convenient form of energy?

2. What is an electric current?

3. What is the unit of current?

4. What is the unit of voltage (also called the potential difference)?

5. What is the unit of resistance?

6. Name an instrument used to measure electric current.

7. Name an instrument used to measure voltage.

8. Name an instrument used to measure resistance.

9. What two conditions are required in order for current to flow in a circuit?

10. List three effects of an electric current.

11. Draw a diagram of the apparatus used to demonstrate each of the three affects of an electric current.

12. Name one everyday useful application of the heating effect of an electric current.

13. Name one everyday useful application of the magnetic effect of an electric current.

14. What are the three terminals in a plug called?

15. What colour wire is attached to each terminal?

16. What is the function of the earth wire?

17. What is the function of a fuse in a circuit?

18. Which wire is the fuse on, and why?

19. What voltage is mains electricity?

20. A hair-dryer uses 5 amps of electricity. Will it operate if its plug has a 3 A fuse? Give a reason for your answer.

21. The expected current flowing through a certain circuit is 2.4 Amps. Which of the following fuses is most appropriate; 1A, 2 A, 3A, 5A or 13A?

22. Draw the symbol for each of the following underneath the wordResistor Switch Voltmeter Light Bulb Battery Rheostat

23. What is meant by the term ‘Potential Difference’ (or ‘Voltage’) as it applies to a circuit?

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24.(i) You are given a battery and two light-bulbs. (ii) Draw a circuit diagram showing the batteries arranged (i) in parallel, (ii) in series.(iii) Which circuit will be brighter?(iv) In which circuit will the battery last longer?(v) Which circuit is more likely to represent the arrangement of Christmas lights? Why?

25. A battery provides a potential difference of 9 volts across a metallic conductor of resistance 0.5 ohms. Calculate the current flowing through the circuit.

26. Fill in the tableV= IR, P = VI

27. Draw a fully labelled diagram of the apparatus used in the experiment to establish the relationship between potential difference and current.

28. Sketch the graph which you would expect to obtain from this experiment. What does the slope of the graph represent?

29. The measurements made by a student in an experiment to establish the relationship between potential difference and current are shown in the table.

Voltage (V) 1.0 2.0 3.0 4.0 5.0 6.0Current (A) 0.1 0.2 0.3 0.4 0.5 0.6

(i) Use the table to draw a graph – on graph paper - of voltage against current.Put voltage on the Y-axis.

(ii) What is the relationship between potential difference and current? Give a reason for your answer.

(iii) Calculate the resistance of the resistor used in this experiment.

30. Draw a diagram to show how two light bulbs can be connected in series with a battery.

31. Draw a diagram to show how two light bulbs can be connected in parallel with a battery.

32. Why are most light bulbs arranged in parallel instead of in series?

The kilowatt-hour

33. What is the unit of electrical energy used by the E.S.B. on electricity bills?

34. What is the rule used to calculate the number of kilowatt-hours used by an appliance?

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Voltage Current Resistance Power Time kW Hours

Cost per unit

Total cost

200 5 40 1000 2 2 6500 2 3 7

3 25 6220 21000 2500 10

35. Give a typical power rating (in watts) of any electrical appliance that you have at home. Name the appliance.

36. Calculate the cost of running a 2.4kW electric fire for 5 hours if each unit of electricity costs 8 pence.

37. A 600 Watt cooker is on for 30 minutes. If each unit of electricity costs 11 cent, calculate the cost of running the cooker.

69

Physics: 15. Electronics


SyllabusOP57 Understand that a diode is a device that allows current to flow in one direction only, and that a light emitting

diode (LED) requires less current than a bulb

OP58 Set up simple series circuits using switches, buzzers, LEDs and resistors

OP59 Measure the resistance of a light-dependent resistor (LDR) under varying degrees of brightness of light

OP60 Identify everyday applications of the diode, including the LED, and of the LDR

Student Notes

Diodes

The symbol for a diode is shown on the right.The arrow indicates the direction in which current can flow.

Simple series circuits using diodesIn the diagram on the right, current would normally flow in an anti-clockwise direction (from the positive end to the negative end).In this case however current will only flow through part A, and not through part B because the diode in part B is pointing in the wrong direction.

Light Emitting Diodes (LEDs)

They are very important in electronics because they use very little electricity.

Simple series circuits using LEDsNote that in both circuits the current flows in an anti-clockwise direction (can you remember why?).However the LED in the second circuit is turned the wrong way around so no current will flow in the second circuit and no light will be emitted.

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Image Symbol

Image Symbol

A diode is a device that allows current to flow in one direction only

In an electric circuit current flows from the positive end of the battery to the negative end.The positive end is represented with a long solid line, and the negative end is represented with a short solid line.

LEDs are similar to diodes but emit light when current passes through them

Light Dependent Resistors (LDRs)

To measure the resistance of a LDR under varying degrees of brightnessConnect the LDR to an ohmmeter or to a multimeter set to read resistance and slowly cover the LDR from light.Notice that the resistance decreases.

Applications of the diodeAlmost all electronic appliances have diodes inside them which help turn alternating current into direct current.

Applications of the LEDLEDs used to be used primarily as indicators in electronic circuitry (e.g. as standby indicators in televisions, radios etc) but modern diodes can give out a lot of light efficiently and so are now used in many designs of flashlights.

Applications of the LDRTextbooks often mention that LDRs are used to switch on street lights when it gets dark, yet this can seem confusing because the resistance of the LDR is high when it is dark so how can this be responsible for current flowing through the street-light?What actually happens is that this reduced current is detected by a second circuit which in turn uses that information to turn on the street-light.

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Component SymbolA LDR is a resistor whose resistance decreases with increasing light intensity

Exam questions

Diodes and Light Emitting Diodes1. [2008]

Identify the devices shown in the diagram.

2. [2008]Leds are often used instead of bulbs. Give a reason for this wide application.

3. [2006 OL] The diagram shows the symbol of a LED.

(i) Complete the circuit on the right by drawing in the LED so that the LED will light when the switch is closed.

(ii) Why is there a resistor connected in series with the LED?

4. [2007 OL](i) Identify device labelled A on the right.(ii) Complete the circuit inserting the symbol for the device A so that the buzzer would

sound if the switch were closed.

5. [2007](i) Look carefully at the circuit diagram and then state which bulb/s, if any, light

when the switch is closed.(ii) Give a reason for your answer.

6. [2006]A pupil carried out an investigation into the effect of a diode on d.c. and on a.c. circuits using an LED. The following circuits were initially set up.

(i) What is observed in circuit A (the first circuit) and in circuit B (the second circuit)?

(ii) When the batteries in circuits A and B were replaced by 6 V a.c. supplies the LEDs glowed dimly in both circuits. Explain this observation.

Light Dependent Resistors7. [2009](i) The diagram shows a light dependent resistor (LDR) and a graph of the resistance of the

LDR against the brightness of light falling on it.Give an everyday use for an LDR.

(ii) Describe an experiment to measure the resistance of an LDR under varying degrees of brightness of light.

(iii) Draw the circuit diagram in the box provided. (iv) Explain how you would vary the brightness of the light.

You do not have to state how the brightness of the light was measured.

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Exam solutions

Diodes and Light Emitting Diodes1. Light emitting diodes (leds)2. They are cheap/ can be switched on and off rapidly without ‘blowing’/ long lasting/ fit into small spaces. 3. (i) Diode inserted in forward bias (i.e. just drop it in without turning it around)(ii) Protect the led / limit current 4.(i) A: Diode (ii) Drop the diode into the circuit as it is (without turning it around).5.(i) Bulb A lights (ii) The diode with A is in forward bias (the + end of diode is connected to + pole of the battery) and so allows current

to flow.6.(i) The LED in circuit A glows while the LED in circuit B does not glow (ii) a.c. is alternating current, so for half the time current is flowing in the right direction and the led glows, but for the

other half of the cycle the current is flowing in the wrong direction and so the led does not glow..

Light Dependent Resistors7.(i) To measure light intensity/ as part of a circuit to switch on (off) lights/ light sensor/ alarms/ street lights/ camera...(ii) Connect the LDR to a multimeter set to measure resistance.

Note the reading on the ohmmeter when the LDR is at different distances from the light bulb.(iii) See diagram (iv) Move light source closer to the LDR and note that the resistance decreases.

Test Questions

1. What is the function of a diode in a circuit?

2. What do the letters LED stand for?

3. What is the function of a LED (Light Emitting Diode)?

4. What do the letters LDR stand for?

5. How does a LDR (Light Dependant Resistor) work?

6. What is the function of a rectifier?

7. Draw the symbol for (i) ldr, (ii) led

8. Give one everyday use of (i) an led, (ii) an ldr.

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junior cert science physics booklet

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