lss module 1 chpt 4 investigating electricity

MODULE 1:GADGETS WORK WONDERS (I)Chapter 4 Investigating Electricity

© Copyright Star Publishing Pte Ltd

Chapter 4 Investigating Electricity

4.1 Why is electricity a useful form of energy?

4.2 Why are electrical appliances made of both conductors and insulators?4.3 What are current, voltage and

resistance? 4.4 What are the differences between

series and parallel circuits?4.5 How can electricity be used safely and

responsibly?


ObjectivesDescribe electricity as a useful

form of energy in our lifeOutline the process from the

production of electricity to using it in our home with reference to the energy conversions that take place


Why is electricity a Useful Form of Energy?Electricity is useful as it

provides energy for electrical appliances.

Electricity is used widely as:

(a) it can be transmitted from one place to another easily using wires and cables.

(b) Electricity can be converted to other forms of energy


electrical appliances

How is electrical energy converted to heat energy? We need different forms of

energy for different purposes.

Electrical appliances convert electricity into the form of energy we need.

When we need heat energy, we use appliances such as electric kettles and electric irons.


appliances that convertelectrical energy to heat energy

Activity Book LinkActivity 4.1Importance of ElectricityActivity 4.2Using Electricity to Produce Heat

How is electrical energy converted to light and/or sound energy?Electricity provides

us with lighting such as by using appliances such as fluorescent lamps.

Appliances like televisions and audio systems convert electricity to light and/or sound energy.


electrical appliances that convert electrical energy to light and/or sound

How is electrical energy converted to mechanical energy?

Washing machines, blenders and electric fans have electric motors that convert electricity to mechanical energy.


electrical appliances that convert electrical energy into mechanical energy

Gadgets and electricity

Mobile phones, portable music players, laptop computers operate on electricity.


handphone

computer

What are the Sources of Electricity?

In Singapore, most of the electricity is produced at the power stations.

The power stations in Singapore use fossil fuels (oil and natural gas) to produce electricity.


the Senoko Power Station is located at the northern part of Singapore

What are the energy conversions in a Power Station?


How is electricity distributed to homes and offices?


What are other Sources of Electricity?

Electricity can also be obtained from batteries which provide us with electrical energy while we are on the move.


different types of batteries

Solar energy Some rural areas are too

far out to receive electricity from power stations and depend on solar energy.

Solar panels on top of some buildings provide electricity.

However, they provide a limited amount of electricity.


solar panels provide electricity in rural areas

Solar panels installed on topof buildings

Activity Book LinkActivity 4.4How Electricity is Produced



4.2 Why are electrical appliances made of both conductors and insulators?

4.3 What are current, voltage and resistance?

4.4 What are the differences between series and parallel circuits?

4.5 How can electricity be used safely and responsibly?


ObjectivesRelate the electrical conducting

properties of materials to their use in the various parts of electrical appliances/circuits

Investigate and classify a variety of materials as insulators or conductors


Electrical conductors and insulators

Materials can be classified into electrical conductors and electrical insulators.


electricity does not passthrough every part of a

hairdryer

copper is commonlyused to make wires

What are electrical conductors?

Electrical conductors are materials that allow electricity to pass through them.

The most commonconductors are metals such as copper and aluminium.


aluminium is used to make power lines

What are electrical insulators?Electrical

insulators are materials that do not allow electricity to pass through them.

Examples are plastics, rubber, wood, glass and paper.


Are there non-metals that conduct electricity?

Examples of non-metals that conduct electricity is graphite, a form of carbon found in pencil lead.

Acids and salt solutions are other examples of non-metals that conduct electricity


examples of non-metals that conduct

electricity

Using Electrical Conductors andInsulators We can find both

conductors and insulators in electrical appliances.

Conductors are used to conduct electricity so that electrical appliances can function.

Insulators are used to prevent electricity from flowing to places that we do not want it to reach.


a hairdryer is made of bothconductors

and insulators

copper wires are insulated with plastic

covers

Activity Book LinkActivity 4.5Electrical Conductors and Insulators






responsibly?


ObjectivesExplain what is meant by current,

voltage and resistance and state their units

Use a voltmeter/ammeter for electrical measurements


What is Current?

In the above, the bulb lights up because there is an electric current flowing from the positive (+) terminal of the battery to the negative (–) terminal


current in the circuit causesthe bulb to light up

How do we measure current? We measure current with an

ammeter.

Ammeters should be connected in series.

The ammeter has two terminals:

(a) The positive terminal should be connected to the positive terminal of the battery.

(b) The negative terminal should be connected nearer to the negative terminal of the battery.


an ammeter

What is SI unit of electric current?

The SI unit of electric current is the ampere (A).

A current of 2 amperes is written as 2 A.


Activity Book LinkActivity 4.6Measuring Current

What is voltage?

Voltage provides the energy for current to flow

We can understand voltage by thinking of a water pump pumping water around a circular pipe. When the pump is removed, the water stops flowing.


a water pump pumps water around a

circular pipe

a dry cell provides energy for

current to flow

How do we measure voltage?To measure the

voltage between two points in an electric circuit, an instrument called the voltmeter is used.

Voltmeters should be connected in parallel.


voltmeters are connectedin parallel

What is the SI unit of voltage?The SI unit of voltage is the volt (V).

A voltage of 1.5 volts is written as 1.5 V.


Activity Book LinkActivity 4.7Measuring VoltageActivity 4.8Voltage and Current

Cells in series

A common dry cell usually provides 1.5 V of voltage.

To get a higher voltage, we can join two or more dry cells by connecting the ‘+’ terminal of a cell to the ‘–’ terminal of another cell as shown below.


What is Resistance?Resistance is

something that opposes the flow of current.

All electrical components have resistance.

Some components have higher resistance than others.


copper wires have very low resistance

light bulbs have higher resistance

How is resistance related tothe current?


The higher the resistance in a circuit, the smaller the current.

Circuit A has a higher resistance than Circuit B, therefore the current in Circuit A is smaller.

What is resistance?


Water flows quickly when there is nothing to block it (low resistance)

Water flows slower when there is something blocking it (high resistance)

We can better understand resistance by looking at how water flows.

What is a resistor? A resistor is an electrical

component that provides resistance.

There are two types of resistors — fixed resistor and variable resistor.

The resistance of a fixed resistor cannot be changed.

The resistance of a variable resistor can be adjusted, usually by turning a knob or moving a slider.


a fixed resistor

two types of variable resistors

How do we measure resistance?Resistance can be

measured using a multimeter set to resistance mode.

The SI unit of resistance is the ohm (Ω).

A resistance of 10 ohms is written as 10 Ω.


a multimeter can beused to measure resistance.

What are the uses of resistors?

Resistors are widely used in electrical appliances such as radios, televisions, and computers to obtain the current needed for them to work properly.


resistors adjust current flowing through appliances






responsibly?


ObjectivesIdentify series and parallel circuitsExplain why parallel circuits are

widely used in household while series circuits are not

Draw and interpret circuit diagrams and set up circuits comprising electrical sources (cell and battery), switches, lamps, resistors (fixed), ammeters and voltmeters


What is an electric circuit?An electric circuit is a path for

current to flow.


current flows through an electric circuit

Open and closed circuits


an open circuit with no current

a closed circuit with current

Current will only flow in a closed circuit.

What is a series circuit?

In a series circuit, the electric components are connected as a single path.

If one of the bulbs is removed or blown, the circuit will be opened. The other two bulbs will not light up.

This is why it is not advisable to connect the lights in our homes in series. © Copyright Star Publishing

Pte Ltd

a series circuit

What is a series circuit?


Traffic flows on an one-lane bridge

Traffic stops when one part of a bridge collapses

A series circuit is like a bridge with only one lane.

When one part of the bridge collapses, the traffic will stop.

What is a parallel circuit? In a parallel circuit, the

electrical components are connected to form two or more paths.

When one of the bulbs is removed or blown, the other two bulbs will not be affected.

This is why the lights in our homes are connected in parallel.


a parallel circuit

What is a parallel circuit?


A parallel circuit is like a road with two separate lanes. When one of the lanes is blocked, traffic can still pass through the other lane.

traffic continues on the lane that is not blocked

Circuit Symbols


To make drawing of electrical circuits simple, symbols representing electric parts are used.

Circuit diagrams


a circuit with a cell, two bulbs connected in series and an open switch

a circuit with a cell, two bulbs connected in parallel and a closed switch

Activity Book LinkActivity 4.9Electric Circuits





series and parallel circuits?4.5 How can electricity be used safely

and responsibly?


ObjectivesState the hazards of using electricity in

the following situations:▲Damaged insulation▲Overloaded circuits▲Damp conditions

List some precautionary measures to ensure the safe use of electricity

State the importance of reducing electrical energy wastage

Appreciate the importance of using electrical energy responsibly and safely


What are the Hazards of Using Electricity?Electricity, if it is

not used properly, electricity can cause harm or even kill.

The voltage of our mains is 230 V. This is considered a high voltage that is dangerous.


the mains supply in Singapore is 230 V.

Common electrical hazardsThere are three common

electrical hazards:

(a) damaged insulation,(b) overloaded circuits, and(c) damp conditions.


Electrical hazards


Safety FeaturesThere are safety features in our home

electrical system to protect us against the dangers of electricity.


circuit breakers cut off electricity to thehouse (or part of the

house) when the current

becomes too big

fuses melt and cut off electricity to

electricalappliances when

the current becomes too big

earth wires protect us against electric

shockwhen the metal

casing of an electrical appliance

comes in contact with a high voltage

Why is it important to reduce Electrical Energy Wastage?It is important for us to reduce wastage

of electricity energy because:

(a) Singapore depends heavily on fossil fuels imported from other countries to produce electricity;

(b) fossil fuels will be gone forever once they are used;

(c) burning of fossil fuels causes pollution.


What are ways to reduce wastage of electrical energy?Use energy saving lamps instead of filament

lamps.

Use natural light and ventilation

Use electric fans instead of air conditioners.

Choose appliances which are energy efficient

Find out the electrical appliances that use a lot of energy and reduce the time they are used.


an energy saving lamp

lss module 1 chpt 4 investigating electricity

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