ud 1 electricity 3ºeso 13 14.es.en

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ELECTRICITY

Luis García Molina. I.E.S Serra Perenxisa. Torrente (Valencia). 2013

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INTRODUCTION

-I.OHM´S LAW: serial and parallel formulas

-II. ELECTRICITY

III. ELECTRIC POWER

-IV.DIRECT AND ALTERNATING CURRENT

-V.ELECTROMAGNETISM


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ELECTRICAL CONDUCTIVITY AND ATOMS

Matter is made up of atoms (made of nucleus and electrons)

The electric current is moving electrons.

The electrons in the atom are arranged in layers.

To be an electric current the electrons of the valencia layer must jump to the the conductive layer, from where they can run. When jumpong, they leave gaps in the valencia layer that can receive new incoming electrons .

THE CONDUCTIVE MATERIALS have many proper driving electrons and holes, so there can be electric current.

THE INSULATION MATERIALS have no electron conduction because the valence layer is full, with no gaps and so no movement of electrons.

The SEMICONDUCTOR MATERIALS have a few electrons and holes. This materials are doped with other atoms that add electrons or holes. The resolt is that we can generate a electric current “a la carte”.

CORE

ELECTRON

Valence shell

DRIVING LAYER


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CHEMICAL GENERATORS: BATTERIES Electricity is the movement of electrons.

• Chemical generators create electricity from approaching two

different compounds: the one which gives the elecrons and the

one which receive them. They are the batteries (and some can

some can be recharged by plugging)

• Zinc-carbon battery. (Normal battery pack)

• Zinc-mercury battery (button cells)

• Oxid Lead-Sulfate lead battery (car batteries)

• Nickel-cadmium battery.

• Hydrogen Battery

• Lithium ion battery (Li-ion)

• Battery Nickel Metal Hybrid (NiMH)

A substance that gives electrons

A substance that takes electrons

electrons

Electrolyte electrons

If the cable together with the electrons are on cable and we can

use


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ELECTROMAGNETIC GENERATORS: ALTERNATOR

• Iteration between electricity and magnetism: If we move an

electric metal wire between two magnets, the elecrons of the

metal are set in motion, generating an electricity current.

• All we have to do is get something that rotates the wire

Electric wire

electrons

S

N

MAGNET

N

electrons

S

Electric wire

ACT 4: How would you rotate the wire to generate electricity?


II.2 ELECTRIC BATTERY

DOWNLOAD

In these cells, the anode element (XH) is separated as follows:

XH X+ H+ + e-

• The electrons (e-) are used to run the engine

• The positive ion (H+) migrates to the cathode through an intermediate membrane (electrolite)

At the cathode, the positive ions and electrons are coupled with an element (Y) to form YH.

Y + H + e- YH RECHARGE.

With the power of a electricity generator the process is reversed and the battery is ready to be used again

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e- e-

anode - (XH)

cathode + (Y)

engine

e- e-

process

Charging

process

discharge

XH

H + H +

Y

Y H + H +

X

YH

YH

X

XH

TYPES: •Lithium ion battery (Li-Ion)

•Battery Nickel-Metal Hydride (NiMH) Luis García Molina. I.E.S Serra Perenxisa. Torrente (Valencia). 2013

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OHM'S LAW To understand Ohm's law we have to review the 3 fundamental

physical magnitudes of electricity ...

• ACTIVITY 0.1:Complete the following table.

Magnitude and symbol

Unit of measure and

symbol

Definition

Measuring instrument and symbol

Instructions for measuring

Intensity (I)

• Remember Ohm's law: – More voltage-more intensitiy. – More resistance- less intensity. – All this is expressed in a physical-mathematical formula

that George Simon Ohm discovered:

Voltage (V)

Resistance (R)

V I = R Luis García Molina. I.E.S Serra Perenxisa. Torrente (Valencia). 2013

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I.1-OHM'S LAW: FORMULAS CIRCUITS IN SERIES

-I.LEY OF OHM: serial and parallel

formulas

-II. ELECTRICITY

ELECTRIC POWER-III

-IV.CORRIENTE dc or ac

-V.ELECTROMAGNETISMO


series connection • The series connection is to put the receivers in a row.

Ie, the output of the first is connected to the input of the next.

• The problem of serial connection is that the two bulbs share the battery voltage and light power of each bulb is low.

Note that:

> Intensity : through each bulb is the same.

> Resistance: the total of the two lamps at a time is the sum of the resistances of each bulb separately.

> Voltage: the stack is shared between the bulbs, depending on each resistance value. If they have the same strength is shared in same parts. But if one has more resistance used more voltage than the other.

intensity

Vtotal

½ Vtotal ½ Vtotal


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• Let the SERIES CONNECTION.

– The intensitiy through the lamps is the same and is equal to the total intensity of the circuit.

– The total resistance of the two bulbs is equal to the sum of the resistance of each.

– The total voltage of the circuito is distributed between the bulbs according to its resistance: more resistance more part of the total voltage.

vTotal number = V1 + V2

RTotal number = R1 + R2

ITotal number = I1 = I2


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OHM'S LAW MAY APPLY TO EACH SEPARATE CIRCUIT ELEMENT OR AT ALL THE CIRCUIT AT A TIME.

-IF YOU APPLY THE LAW TO THE BULB 1:

-IF YOU APPLY THE LAW TO THE BULB 2: -IF YOU APPLY THE LAW TO THE TOTAL CIRCUIT:

Vbulb1

Ibulb1 = Rbulb1

Bulb 1 Bulb 2

Vbulb2

Ibulb2 = Rbulb2

Vtotal

Itotal = Rtotal


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• ACTIVITIES 1.1:a) Calculated using Ohm's law the value of the total voltage of the battery in the following circuit:

As we speak TOTAL voltage for the circuit to do it ALL have to calculate the resistance value of the total of all the circuit (of the two bulbs at once)

• b) Now calculate the voltage using each bulb separately.

As we speak now of the voltage of each bulb IN PARTICULAR, we must calculate the resistance of

Each bulb.

• C) Verifies that the sum of the voltage of each bulb is equal to

total.

ACTIVITY 1.2: Perform the same calculations as the previous problem for a circuit of 3 BULBS IN SERIES, 1200 , 3400 and 10800 resistance respectively. The total intensity is the same, 0.03 A.

Itotal = 0.03 A

200 100


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I.2-OHM'S LAW: FORMULAS PARALLEL CIRCUIT


formulas

-II. ELECTRICITY

ELECTRIC POWER-III




parallel connection • There is another possibility for connecting the bulbs: as

two independent circuits: With this solution the two bulbs each use ALL the battery voltage and light at maximum

• We can connect the bulbs also this way: to connect the two inputs of the bulbs to each other and the two outputs between them. So it is a parallel connection.


parallel connection

Note that now:

• intensity is divided between the two roads leading to the two bulbs. The more the resistance of each bulb, the less intensity passes through. In fact, if they have the same resistance the intensity is exactly the same, the half of the total.

• resistance The total is A DIFFERENT VALUE THAN the sum of the resistance of the two bulbs. On the next page will see your formula.

• The voltage of each bulb is the same than the total of the circuit.

Itotal

Vtotal

Vtotal

Itotal

½ I total

½ I total


• Let´s see the parallel connection

– The total intensity:

– The total resistance

– The voltatge total:

Itotal Ipereta1

Ipereta2

Itotal

vTotal parallel = V1 = V2= ... = Vn

R1 x R2 RTotal parallelfor2 =

R1+ R2

1

RTotal parallel =

1 + 1 + ... + 1 R1 R2 Rn

ITotal parallel = I1 + I2+ ... + In


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OHM'S LAW MAY APPLY TO EACH SEPARATE CIRCUIT ELEMENT OR ALL THE TRACK AT A TIME.

-IF YOU APPLY TO HAVE THE BULB 1:

-IF YOU APPLY TO HAVE THE BULB 2: -IF YOU APPLY TO ALL THE TRACK:

Vbulb1

Ibulb1 = Rbulb1

Vbulb2

Ibulb2 = Rbulb2

Vtotal

Itotal = Rtotal

Bulb 1

Bulb 2


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• ACTIVITY 1.3 : We will use Ohm's law for a circuit connected in parallel:

– Calculated using Ohm's law the current flowing through the bulb 1.

– I calculated the bulb 2.

– Calculate the voltages of the bulbs 1 and 2.

– Calculate now the total current in the circuit.

• ACTIVITY 1.4 : Perform the same calculations as above but for a circuit similar CASE BUT WITH 3 BULBS IN PARALLEL, resistors 1000 , 2500 and 7250 arespectivamente.

200

100


To solve the mixed circuits we have to look at the overall distribution of the resistors.

• If the overall structure is in series first calculate the value of the equivalent resistances of the resistors in paralalelo. Then do the final calculations in series.

• If the structure is generally parallel first calculate the value of resistencies equivalent of resistors in series in each branch. Then do the final calculations in parallel.

Mixed connection

1.5 Activitat a) Calculate the value of the total circuit resistance b) What is the total current passing through the circuit?

1.6 Activitat a) Calculate the value of the total circuit resistance b) What is the total current passing through the circuit?


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II-ELECTRIC ENERGY


formulas

-II. ELECTRICITY

ELECTRIC POWER-III




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ELECTRICITY

• The bulbs use electricity to produce light. Light is light energy.

• Electric motors electrical energy used to produce movement. The movement is kinetic energy.

• Electric stoves use electricity to produce heat. Heat is thermal energy.


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POWER CONSUMPTION

• In what units is measured electrical energy?

• We can see in our home electricity bill. At the end of the month we spent in our house a certain amount of energy.

– (This is independent of whether it was all in a single day or spread throughout the month)

• THE POWER IS MEASURED IN Kilowatt-hours (KW x h)

– This is because the unit of electrical energy.

– Other units of energy: calorie (cal), July (J)

E = P x t

E = V x I x T

E = R x I2x t

E: Electricity (KW x h) Q: electric power (KW /) T: time (hour)

E: Electricity (July) V: voltage (V) I: intensity (A) T: time (sec)

E: Electricity (July) A: RESISTANCE (ohm) I: intensity (A) T: time (sec) Luis García Molina. I.E.S Serra Perenxisa. Torrente (Valencia). 2013

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POWER CONSUMPTION

ACTIVITY 2.1: Calculates the power consumed by a circuit formed by a 9V battery and 4 resistors in series, 120, 240, 300 and 1230 ohms respectively.

ACTIVITY 2.2: Calculate how much electricity the household has consumed this month:

– A range of 150 W has been on 5 hours.

– The refrigerator (300 W) has been on 90 hours.

– The TV (70 W) has been on 20 hours.

– 7 bulbs (100 W) have been 70 hours each.

ACTIVITY 2.3: Ask at your house a bill wattage kind that yields power in your home.

Analyze it.

How many KW x hours of energy you have consumed?

How much does each Kw x h?

How much did you pay in total?

Much do you think?


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III-POWER ELECTRIC


formulas

-II. ELECTRICITY

ELECTRIC POWER-III



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E (Energy) P = t (Time)

Difference between energy and power

• A stove "A" gives 1000 calories of thermal energy (heat) for 6 hours. The range "B" gives 1000 calories in 1 hour.

• A) Which of the two stoves has spent more electricity?

• B) Which of the two stoves is more powerful?

– Indeed, what is not normally interested in knowing the amount of electricity you spend a stove or a bulb, but its power, ie how long the day.

• Therefore:

– Electric Power is the amount of energy expended electrical apparatus in a unit time.

Unit: Watt (W)


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Power supply: FORMULA

• The formula to calculate the electrical power is:

• As we did with Ohm's law can be made two comments:

– 1) The formula serves equally well for an entire circuit to a particular device.

• If the entire circuit will the values of V, I total

• If an apparatus to set the values of V and I of the apparatus.

– 2) For mathematical things no other way to write the same

formula.

P = V x I

P = R x I2

(This is because as V = R x I by substituting this value in the first formula V, is P = (R x R) x R, which is equal to P = R x I2)


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Electric Power

• ACTIVITY 3.1: Given the following electrical circuit formed by two lamps in series with a resistor 100 each:

– a) Calculate the power of the first formula bulb1

– b) Calculate the power of the second formula bulb2

– c) Calculate the power circuit.

• ACTIVITY 3.2: Given the following electrical circuit formed by two lamps in parallel, having a resistance of 100 each:

– a) Calculate the power of the first formula bulb1

– b) Calculate the power of the second formula bulb2

– c) Calculate the power circuit.

I = 0.045 A

I = 0.09 A

I = 0.09 A


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IV-CURRENT AND ALTERNATING CURRENT


formulas

-II. ELECTRICITY

ELECTRIC POWER-III




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Generators DC

• Batteries and dynamos are generating a type of electricity called direct current.

– These generators maintain a constant voltage, all the while like.

– Since the force that moves electrons around the same time, the electrons always move at the same speed and in the same direction.

electrons


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Generators AC

• The turbine-alternator is generating a type of electrical current called alternating current.

– These generators maintain a variable voltage. Their energy changes with time. First growing towards positive, then decreases to the same but in reverse.

– Strength changes as well, the electrons are accelerated towards one side, stop and accelerate toward the other side.

electrons


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• ACTIVITY 4.1: Look at these two diagrams representing the variation of voltage (Y axis) over time (X axis) and say which gives direct current and alternating current which.

V

t

V

t


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things of the alternating current

• 1.The power plants and our homes generated and used alternately, rather than continuous. Why?

– Because long-distance transport is cheaper and more efficient because it's a very high voltages. (Up to 400,000 V!)

• To reduce power losses along the way:

power losses = R x I2

I should go down to dismuir losses.

• To reduce voltage drops along the way:

voltage loss = R x I

I agree to lower down the falls.

• Thus, to lower the intensity, maintaining the power ...

I should go much V!.

V FOR UP ONLY BE DONE WITH USING AC POWER TRANSFORMERS

p I = V


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– 2. GENERATION AND TRANSPORT OF THE CURRENT. Alternating electric current is generated in the alternator of

different power stations. The generator is basically a turbine d'mou electromagnetic generator or alternator. The difference between them Elèctriques Centrals (wind, solar, nuclear, thermal, etc.). Tipus font is the natural energy mou d'turbine.

Altern is the corrent Elèctric des transports power plant nostres fins to marry them through the Network of transport. Aquesta xarxa is divideix three trams: High Power Surge (200,000 to 400,000 V), mitja Power Surge (10,000 V) i baixa Power Surge (220 V).

T

alternator

transformer 1

Transportation network HIGH

VOLTAGE T

T

Medium voltage network

LOW VOLTAGE Network Transformer 2

transformer 3

turbine


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3. TRANSFORMATION OF AC VOLTAGE

Transformers are the devices which raise and lower blood pressure or voltage. • Those in the transport network, with high tension towers are

very large.

• Those who are within an appliance or electronic device to lower the voltage of 220 V to need the device (5V) are small


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• 4. MODIFICATION OF AC AND CONTINUOUS

Electronic devices use DC and about 5 V. Some get it from your cell or battery. But many are connected to household outlet, as you know is AC 220V and about.

We know that low voltage with a transformer.

We need machines that pass the AC to DC.

RECTIFIERS.

Rectifiers are composed of a diode bridge and a condenser.

Here is the diagram of a rectifier.


alternator

Diode bridge

condenser

Out in continuous


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• 5.The industry-phase alternating current is used.

– If instead of putting this:

– We put this:

We saved a lot of cables (cheapest around) and it works just as well.

It's called because it uses three-phase or 3 phase cables.



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• 6.Vocabulario diagram of sinusoidal alternating

current:

– Frequency: The number of cycles occurring in 1 second. Is f = 50 Hz is 50 cycles per second that!

V

t

1 cycle 1 cycle

Period

Amplitude



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• ACTIVITY 4. 2: Answers

• A) What is the outlet?

• B) What advantages does that explain why use?

• C) What devices use direct current?

• D) What devices use alternating current?

• E) What is the three-phase alternating current?

• F) What are the advantages?

• g) Indicate on the diagram what is the amplitude, period, cycle and frequency?

V

t


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VI-ELECTROMAGNETISM


formulas

-II. ELECTRICITY

ELECTRIC POWER-III




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MAGNETISM • Magnetism is the property that have some materials to

attract ferrous material and attract-repel other magnets.

MAGNETISM WHY?

Magnetism is caused by an arrangement of the electrical charges of the atoms of the material.

+ -

+ -

+ -

+ - - +

Normal material

Magnetic material

As you can guess, ELECTRICITY and magnetism are caused by the movement of electrons. Therefore: Electricity and Magnetism are related. The union of both is called ELECTRO-MAGNETISM. THERE 3 INTERACTIONS BETWEEN FOREIGN-Electricity and Magnetism

N S


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INTERACTION 1

1 Interaction between electricity and magnetism:

A power driver behaves like a magnet.

electrons

= N S

Taking advantage of this effect are constructed ELECTRO: magnets with electrical wires in coil form (increase the power switch)

= N S

- +

- +


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INTERACTION 2


By moving a power line without current in the field of influence of a magnet, it generates (induces) an electric current in the cable.

electrons

=

S

Are constructed so Electromagnetic generators electric power with electric cables and magnets (usually magnets).

N

Since the cable does not move, nothing happens

S N

Since the cable does move the electrons are set in motion


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INTERACTION 3


A magnet (or electromagnet) can move to another.

S

Are constructed so ELECTRIC MOTORS with electromagnets.

N

Opposites attract Poles repel

S S

+

axi

s

stator

rotor

brush

manifold

+

Combining magnet rotor gets a turn


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ACTIVITY 5. 1: Answer

• A) Explain the interaction between electricity and magnetism 1

• B) How does an electromagnet?

• C) Explain the interaction between electricity and magnetism 2

• D) How does an electromagnetic generator?

• E) Explain the interaction between electricity and magnetism 3 F) How does an electric motor?


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ended


ud 1 electricity 3ºeso 13 14.es.en

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