Introducing Electricity

Introducing ElectricityIntroducing Electricity

Textbook pg 52Textbook pg 52

Today’s objectives

• At the end of this lesson, you will be able to:– State the appliances that used

electricity– State the sources of electricity– Define what is electric current

and circuit– Understand the parts of electric

circuit

Think-Pair-ShareThink-Pair-Share Look at the diagrams below:Look at the diagrams below: What are needed for these What are needed for these

appliances to operate?appliances to operate? Could you think of similar Could you think of similar

appliances used for the same appliances used for the same purpose in olden days?purpose in olden days?

You got 2 minutes to share

with someone beside/ behind

you

Electrical AppliancesElectrical Appliances All require electricity to workAll require electricity to work Vacuum cleaner (electricity to Vacuum cleaner (electricity to

kinetic energy)kinetic energy) Lamp (electricity to light energy)Lamp (electricity to light energy) Fan (electricity to kinetic energy)Fan (electricity to kinetic energy)

Electrical AppliancesElectrical Appliances Now we cannot live without Now we cannot live without

electricity.electricity. So many appliances and items So many appliances and items

we used require electricitywe used require electricity

What are the sources of electricity?

• Main electricity• Electric cells• So what’s the difference?

Main Electricity

• Generated by power stations• Delivered to homes and industries

through wires• Finally connected to main sockets• Supplies a lot of electrical energy• Electric shock

Electric Cells

• Used in many portable electrical devices

• Supplies small amount of energy• Safe to touch

Electric Current and Electric Current and Circuit?Circuit? The rate of flow of electric charges The rate of flow of electric charges

is called electric currentis called electric current Electric circuit is the path which the Electric circuit is the path which the

electric current takeselectric current takes

Short video clipShort video clip

Electric circuits - overviewElectric circuits - overview

Parts of a Circuit

• Called electrical components• Examples

– Connecting wires– Bulb– Switch– Electric cell

Connecting wires

• Made of two types of materials• Electrical conductor and electrical

insulatorElectrical

conductor – made of

metal such as copper

Electrical insulator – made of plastic

Connecting wires• Symbols of connecting wires• Connecting wires (joined) and

connecting wires (not joined)• See pg 56

Joined Not joined

Bulb• Symbol of bulb

Switch• Symbol of switch

Close switch

Open switch

Electric Cell• Symbol of electric cell

One electric cell

Two electric cell More than two electric cell

Review QuestionsReview Questions What are the two sources of What are the two sources of

electricity?electricity? Electric cells and main electricityElectric cells and main electricity

The rate of flow of electric charges The rate of flow of electric charges is called an ______________is called an ______________

The path which the electric current The path which the electric current takes is called the _____________takes is called the _____________

What are the 4 parts of circuit we What are the 4 parts of circuit we have covered today?have covered today? Connecting wireConnecting wire BulbBulb SwitchSwitch Electric cellElectric cell

electric current

electric circuit

Match the following:Match the following:

joined connecting wires

bulb

closed switch

one electric cell

SummarySummary What we have learnt today?What we have learnt today?

Uses of electricity in our daily lifeUses of electricity in our daily life Sources of Electricity (Main Sources of Electricity (Main

electricity and electric cells)electricity and electric cells) Define electric current and Define electric current and

electric circuitelectric circuit 4 different parts of circuits and 4 different parts of circuits and

their symbolstheir symbols Connecting wiresConnecting wires BulbsBulbs SwitchSwitch Electric cellElectric cell

Worksheet

Complete the worksheet now

Today’s objectives

• At the end of this lesson, you will be able to:– Understand what is complete

and incomplete circuits– State the different types of

switches in circuits– Understand how circuits can be

arranged

Complete and incomplete Complete and incomplete circuitscircuits Complete circuits is also Complete circuits is also

known as closed circuitsknown as closed circuits Incomplete circuits is also Incomplete circuits is also

known as opened circuitsknown as opened circuits What is the difference between What is the difference between

the two?the two?

Complete/Closed circuitsComplete/Closed circuits It is complete path without any It is complete path without any

gaps from one end of the cell gaps from one end of the cell to the light bulb and back to the to the light bulb and back to the other end of the cellother end of the cell

Incomplete/Open circuitsIncomplete/Open circuits The path is incompleteThe path is incomplete Each circuit has a gap in it and Each circuit has a gap in it and

the bulbs do not light upthe bulbs do not light up Example: no source of Example: no source of

electrical energy or connecting electrical energy or connecting wire is missingwire is missing

See pg 55.See pg 55.

Try Inquiry Time pg 55Try Inquiry Time pg 55 Circuit DCircuit D A: Place a connecting wire on A: Place a connecting wire on

each side of the celleach side of the cell B: Place a connecting wire on B: Place a connecting wire on

each side of the light bulbeach side of the light bulb C: Place a connecting wire C: Place a connecting wire

from the bulb and the cell on from the bulb and the cell on each side of the celleach side of the cell

Using symbols to draw Using symbols to draw circuit diagramscircuit diagrams

Page 56Page 56 Try inquiry timeTry inquiry time Circuit A. However the extra Circuit A. However the extra

line between the two cells is line between the two cells is not necessary. Circuit B is not necessary. Circuit B is different as the light bulb is different as the light bulb is situated between the two cellssituated between the two cells

Types of Switches

• A switch is used to open or close a circuit.

• Tap key switch• A plug switch• A mains switch used in buildings• When switch is off, the circuit is

opened and the bulb will not light up• When switch is on, the circuit is closed

and the bulb will light up

Types of Switches

Ask and Learn

Conductors and Insulators

Ask and Learn

How circuit can be How circuit can be arranged?arranged?

Series circuitSeries circuit Parallel circuitParallel circuit

Series CircuitSeries Circuit

The three light bulbs are The three light bulbs are arranged in seriesarranged in series

Each component is joined one Each component is joined one after the other to form a single after the other to form a single pathpath

Current flows through each Current flows through each component is the samecomponent is the same

Series CircuitSeries Circuit

If one bulb in a series circuit is If one bulb in a series circuit is removed or broken, no current removed or broken, no current flowsflows

The remaining bulbs do not The remaining bulbs do not light uplight up

Because the circuit is openedBecause the circuit is opened

Parallel CircuitParallel Circuit

Any amount of light bulbs are Any amount of light bulbs are arranged in parallelsarranged in parallels

Divides two or more branches Divides two or more branches and has electrical components and has electrical components in each branchin each branch

Parallel CircuitParallel Circuit

The current from the battery divides The current from the battery divides and flows through each branchand flows through each branch

If one bulb breaks or removed, If one bulb breaks or removed, other bulbs on the circuit remain litother bulbs on the circuit remain lit

Because the circuit remains closedBecause the circuit remains closed

Series and Parallel Series and Parallel CircuitCircuit

Ask and LearnAsk and Learn

Do Check PointDo Check Point

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ObjectivesObjectives

At the end of this lesson, you At the end of this lesson, you will be able to:will be able to: Understand what is electric Understand what is electric

current and how to measure current and how to measure electric currentelectric current

Understand what is voltage and Understand what is voltage and how to measure voltagehow to measure voltage

State the different voltages for State the different voltages for different sourcesdifferent sources

Understand how electric cells are Understand how electric cells are connected in electrical connected in electrical appliancesappliances

Electric CurrentElectric Current

Flow of electric chargesFlow of electric charges This flow of electrons in one This flow of electrons in one

directions in a circuit is called directions in a circuit is called an electric currentan electric current

Electrons require energy in Electrons require energy in order to moveorder to move

Energy come from the electric Energy come from the electric cell in the circuitcell in the circuit

Electric cell has two terminalsElectric cell has two terminals

Electric CurrentElectric Current

Positive and negativePositive and negative Pushes electrons out of the Pushes electrons out of the

negative terminal and round negative terminal and round the circuitthe circuit

Flow back to the positive Flow back to the positive terminal of the cellterminal of the cell

Electrons are not used up only Electrons are not used up only energy is used upenergy is used up

Video on Electric Video on Electric CurrentCurrent

Short videoShort video

Measuring Electric CurrentMeasuring Electric Current

AmmeterAmmeter SI unit for electric current is SI unit for electric current is

ampere (A)ampere (A) 1A = 1000 mA1A = 1000 mA 1mA = 0.001A1mA = 0.001A Connected in seriesConnected in series


Ask and LearnAsk and Learn


What is Voltage?What is Voltage?

To measure the energy the To measure the energy the electrons receiveelectrons receive

An electron can have a large An electron can have a large amount of potential energy at one amount of potential energy at one point in the circuitpoint in the circuit

It can also have a low amount of It can also have a low amount of potential energy at another pointpotential energy at another point

The difference in potential energy The difference in potential energy between the two points is known as between the two points is known as voltagevoltage

What is Voltage?What is Voltage?

SI unit for voltage is volt (V)SI unit for voltage is volt (V)

Measuring VoltageMeasuring Voltage

VoltmeterVoltmeter

VoltmeterVoltmeter

Connected in parallel across Connected in parallel across the cellthe cell

Has positive (red) terminal and Has positive (red) terminal and a negative (black) terminal like a negative (black) terminal like ammeterammeter

Positive terminal connected to Positive terminal connected to the positive side of the cellthe positive side of the cell

Negative terminal connected to Negative terminal connected to the negative side of the cellthe negative side of the cell

Measuring VoltageMeasuring Voltage

VoltmeterVoltmeter

Different voltage for Different voltage for different electric sourcesdifferent electric sources Different electric cell have Different electric cell have

different voltagedifferent voltage In Singapore the main voltage In Singapore the main voltage

is 230Vis 230V

1.5V9V

12V

How are electric cells connected How are electric cells connected in electrical appliances?in electrical appliances? Electric cells are connected in Electric cells are connected in

series with the positive terminal series with the positive terminal of one cell touching the of one cell touching the negative terminal of the next negative terminal of the next cellcell

The total voltage across all the The total voltage across all the electric cells is equal to the electric cells is equal to the sum of the voltages of the sum of the voltages of the individual cellsindividual cells

How are electric cells connected How are electric cells connected in electrical appliances?in electrical appliances? For example you have electric For example you have electric

cell of 1.5Vcell of 1.5V If the toy need 9V to work.If the toy need 9V to work. You will need six 1.5V electric You will need six 1.5V electric

cellscells

CheckpointCheckpoint

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At the end of this lesson you At the end of this lesson you will be able to:will be able to: State what is a resistorState what is a resistor Understand the different types of Understand the different types of

resistorsresistors Understand how resistors is Understand how resistors is

placed in series and parallel placed in series and parallel arrangementsarrangements

What is a resistor?What is a resistor?

Appliances need to ensure that Appliances need to ensure that the correct size of current flows the correct size of current flows to operate properlyto operate properly

To control the size of the To control the size of the current, electrical components current, electrical components called resistors are used in the called resistors are used in the circuitscircuits

ResistorsResistors

AsknLearnAsknLearn

Types of resistorsTypes of resistors

FixedFixed VariableVariable

Fixed ResistorsFixed Resistors

One fixed resistanceOne fixed resistance Resistance can be a fraction of Resistance can be a fraction of

an ohm to thousands of ohmsan ohm to thousands of ohms SI unit is ohmsSI unit is ohms

Variable ResistorsVariable Resistors

Known as rheostatKnown as rheostat Vary the resistance in a circuitVary the resistance in a circuit Resistance change, the current Resistance change, the current

also changesalso changes When resistance decreases, When resistance decreases,

the current increasesthe current increases

RheostatsRheostats

Different types for different Different types for different purposespurposes

Fixed and Variable Fixed and Variable ResistorResistor

AsknLearnAsknLearn

Arrangement of resistorsArrangement of resistors

Can be in series or parallelCan be in series or parallel SeriesSeries

Same current from the electric Same current from the electric cell passes through each resistor cell passes through each resistor

As more resistors are added, the As more resistors are added, the resistance to flow electrical resistance to flow electrical charges increasescharges increases

The current in the circuit The current in the circuit decreasesdecreases

Overall resistance in series Overall resistance in series circuit increasescircuit increases

Arrangement of resistorsArrangement of resistors

ParallelParallel For resistors in parallel, current For resistors in parallel, current

from the electric cell divided from the electric cell divided among the resistoramong the resistor

More resistors added more More resistors added more electrical charges are able to electrical charges are able to flow through the resistors at the flow through the resistors at the same timesame time

Current in circuit increasesCurrent in circuit increases Overall resistance of the parallel Overall resistance of the parallel

circuit decreasescircuit decreases

Metal with…Metal with…

Low resistanceLow resistance Copper and silverCopper and silver

High resistanceHigh resistance NichromeNichrome

Resistor – Series and Resistor – Series and Parallel Parallel

AsknLearnAsknLearn

CheckpointCheckpoint

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At the end of this lesson, you At the end of this lesson, you will be able to:will be able to: State the heating effects and State the heating effects and

examplesexamples Understand what is Understand what is

electromagnets and its useselectromagnets and its uses Understand what is chemical Understand what is chemical

effects and electroplatingeffects and electroplating

Effects of Electric CurrentEffects of Electric Current

Heating effectHeating effect Magnetic effectMagnetic effect Chemical effectChemical effect

Heating EffectHeating Effect

Resistance in circuit wires Resistance in circuit wires affects the amount of electric affects the amount of electric current flowingcurrent flowing

Electric current flows through Electric current flows through the wire, the wire gets heated the wire, the wire gets heated upup

Electrical energy to heat Electrical energy to heat energyenergy


Heating element in an Heating element in an electrical appliance consists of electrical appliance consists of high resistance wires such as high resistance wires such as nichromenichrome Very hotVery hot Produce more heatProduce more heat

Connecting wires are made of Connecting wires are made of low resistance materials such low resistance materials such as copperas copper Less hotLess hot Produce less heatProduce less heat


If resistance wire gets very hot, If resistance wire gets very hot, light can also be producedlight can also be produced

Example: Filament of an Example: Filament of an electric light bulbelectric light bulb

Magnetic EffectMagnetic Effect

Electric current also produces Electric current also produces magnetic effectmagnetic effect

Example: placing wire near Example: placing wire near compass needle and let compass needle and let electric current flow, the needle electric current flow, the needle will movewill move


ElectromagnetElectromagnet Coil of wire usually wound Coil of wire usually wound

around a piece of ironaround a piece of iron When current flows, it acts like a When current flows, it acts like a

bar magnetbar magnet If no current flow, the If no current flow, the

electromagnet loses its electromagnet loses its magnetismmagnetism


ElectromagnetElectromagnet How to make it stronger?How to make it stronger?

Increase the current in the coilIncrease the current in the coil Increase the number of turns of Increase the number of turns of

wire in the coilwire in the coil Winding the coil around an iron Winding the coil around an iron

corecore


ElectromagnetElectromagnet UsesUses

Magnetic cranesMagnetic cranes Electric bellsElectric bells Electric motorsElectric motors

Chemical EffectChemical Effect

ElectrolysisElectrolysis UsesUses

ElectroplatingElectroplating Extraction of some metalsExtraction of some metals

ElectroplatingElectroplating

Watch videoWatch video

Chemical EffectChemical Effect

Extraction of metalsExtraction of metals Solid compound of the metal is Solid compound of the metal is

heated until it meltsheated until it melts An electric current is then An electric current is then

passed through the molten passed through the molten compoundcompound

Molten compound break down to Molten compound break down to give the metalgive the metal

Do CheckpointDo Checkpoint

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Introducing Electricity