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1. Introducing ElectricityIntroducing Electricity
Textbook pg 52Textbook pg 52

2. 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

3. Think-Pair-ShareThink-Pair-Share
 Look at the diagrams below:Look at the diagrams below:
 What are needed for theseWhat are needed for these
appliances to operate?appliances to operate?
 Could you think of similarCould you think of similar
appliances used for the sameappliances used for the same
purpose in olden days?purpose in olden days?
You got 2
minutes
to share
with
someone
beside/
behind
you

4. Electrical AppliancesElectrical Appliances
 All require electricity to workAll require electricity to work
 Vacuum cleaner (electricity toVacuum 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)

5. Electrical AppliancesElectrical Appliances
 Now we cannot live withoutNow we cannot live without
electricity.electricity.
 So many appliances and itemsSo many appliances and items
we used require electricitywe used require electricity

6. What are the sources of electricity?
• Main electricity
• Electric cells
• So what’s the difference?

7. 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

8. Electric Cells
• Used in many portable electrical
devices
• Supplies small amount of energy
• Safe to touch

9. Electric Current andElectric Current and
Circuit?Circuit?
 The rate of flow of electric chargesThe rate of flow of electric charges
is called electric currentis called electric current
 Electric circuit is the path which theElectric circuit is the path which the
electric current takeselectric current takes

10. Short video clipShort video clip
Electric circuits - overviewElectric circuits - overview

11. Parts of a Circuit
• Called electrical components
• Examples
– Connecting wires
– Bulb
– Switch
– Electric cell

12. Connecting wires
• Made of two types of materials
• Electrical conductor and electrical
insulator
Electrical
conductor –
made of
metal such as
copper
Electrical
insulator –
made of
plastic

13. Connecting wires
• Symbols of connecting wires
• Connecting wires (joined) and
connecting wires (not joined)
• See pg 56
Joined Not joined

14. Bulb
• Symbol of bulb

15. Switch
• Symbol of switch
Close switch
Open switch

16. Electric Cell
• Symbol of electric cell
One electric cell
Two electric cell More than two electric cell

17. Review QuestionsReview Questions
 What are the two sources ofWhat are the two sources of
electricity?electricity?
 Electric cells and main electricityElectric cells and main electricity
 The rate of flow of electric chargesThe rate of flow of electric charges
is called an ______________is called an ______________
 The path which the electric currentThe path which the electric current
takes is called the _____________takes is called the _____________
 What are the 4 parts of circuit weWhat 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

18. Match the following:Match the following:
joined connecting
wires
bulb
closed switch
one electric cell

19. 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 (MainSources of Electricity (Main
electricity and electric cells)electricity and electric cells)
 Define electric current andDefine electric current and
electric circuitelectric circuit
 4 different parts of circuits and4 different parts of circuits and
their symbolstheir symbols
 Connecting wiresConnecting wires
 BulbsBulbs
 SwitchSwitch
 Electric cellElectric cell

20. Worksheet
Complete the worksheet now

21. 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

22. Complete and incompleteComplete and incomplete
circuitscircuits
 Complete circuits is alsoComplete circuits is also
known as closed circuitsknown as closed circuits
 Incomplete circuits is alsoIncomplete circuits is also
known as opened circuitsknown as opened circuits
 What is the difference betweenWhat is the difference between
the two?the two?

23. Complete/Closed circuitsComplete/Closed circuits
 It is complete path without anyIt is complete path without any
gaps from one end of the cellgaps from one end of the cell
to the light bulb and back toto the light bulb and back to
the other end of the cellthe other end of the cell

24. Incomplete/Open circuitsIncomplete/Open circuits
 The path is incompleteThe path is incomplete
 Each circuit has a gap in it andEach circuit has a gap in it and
the bulbs do not light upthe bulbs do not light up
 Example: no source ofExample: no source of
electrical energy or connectingelectrical energy or connecting
wire is missingwire is missing
 See pg 55.See pg 55.

25. Try Inquiry Time pg 55Try Inquiry Time pg 55
 Circuit DCircuit D
 A: Place a connecting wire onA: Place a connecting wire on
each side of the celleach side of the cell
 B: Place a connecting wire onB: Place a connecting wire on
each side of the light bulbeach side of the light bulb
 C: Place a connecting wireC: Place a connecting wire
from the bulb and the cell onfrom the bulb and the cell on
each side of the celleach side of the cell

26. Using symbols to drawUsing symbols to draw
circuit diagramscircuit diagrams
 Page 56Page 56
 Try inquiry timeTry inquiry time
 Circuit A. However the extraCircuit A. However the extra
line between the two cells isline between the two cells is
not necessary. Circuit B isnot necessary. Circuit B is
different as the light bulb isdifferent as the light bulb is
situated between the two cellssituated between the two cells

27. 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

28. Types of Switches
Ask and Learn

29. Conductors and Insulators
Ask and Learn

30. How circuit can beHow circuit can be
arranged?arranged?
 Series circuitSeries circuit
 Parallel circuitParallel circuit

31. Series CircuitSeries Circuit
 The three light bulbs areThe three light bulbs are
arranged in seriesarranged in series
 Each component is joined oneEach component is joined one
after the other to form a singleafter the other to form a single
pathpath
 Current flows through eachCurrent flows through each
component is the samecomponent is the same

32. Series CircuitSeries Circuit
 If one bulb in a series circuit isIf one bulb in a series circuit is
removed or broken, no currentremoved or broken, no current
flowsflows
 The remaining bulbs do notThe remaining bulbs do not
light uplight up
 Because the circuit is openedBecause the circuit is opened

33. Parallel CircuitParallel Circuit
 Any amount of light bulbs areAny amount of light bulbs are
arranged in parallelsarranged in parallels
 Divides two or more branchesDivides two or more branches
and has electrical componentsand has electrical components
in each branchin each branch

34. Parallel CircuitParallel Circuit
 The current from the battery dividesThe 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

35. Series and ParallelSeries and Parallel
CircuitCircuit
Ask and LearnAsk and Learn

36. Do Check PointDo Check Point
Page 59Page 59

37. ObjectivesObjectives
 At the end of this lesson, youAt the end of this lesson, you
will be able to:will be able to:
 Understand what is electricUnderstand what is electric
current and how to measurecurrent and how to measure
electric currentelectric current
 Understand what is voltage andUnderstand what is voltage and
how to measure voltagehow to measure voltage
 State the different voltages forState the different voltages for
different sourcesdifferent sources
 Understand how electric cells areUnderstand how electric cells are
connected in electricalconnected in electrical
appliancesappliances

38. Electric CurrentElectric Current
 Flow of electric chargesFlow of electric charges
 This flow of electrons in oneThis flow of electrons in one
directions in a circuit is calleddirections in a circuit is called
an electric currentan electric current
 Electrons require energy inElectrons require energy in
order to moveorder to move
 Energy come from the electricEnergy come from the electric
cell in the circuitcell in the circuit
 Electric cell has two terminalsElectric cell has two terminals

39. Electric CurrentElectric Current
 Positive and negativePositive and negative
 Pushes electrons out of thePushes electrons out of the
negative terminal and roundnegative terminal and round
the circuitthe circuit
 Flow back to the positiveFlow back to the positive
terminal of the cellterminal of the cell
 Electrons are not used up onlyElectrons are not used up only
energy is used upenergy is used up

40. Video on ElectricVideo on Electric
CurrentCurrent
Short videoShort video

41. Measuring Electric CurrentMeasuring Electric Current
 AmmeterAmmeter
 SI unit for electric current isSI unit for electric current is
ampere (A)ampere (A)
 1A = 1000 mA1A = 1000 mA
 1mA = 0.001A1mA = 0.001A
 Connected in seriesConnected in series

42. Measuring Electric CurrentMeasuring Electric Current

43. Ask and LearnAsk and Learn
Measuring Electric CurrentMeasuring Electric Current

44. What is Voltage?What is Voltage?
 To measure the energy theTo measure the energy the
electrons receiveelectrons receive
 An electron can have a largeAn electron can have a large
amount of potential energy at oneamount of potential energy at one
point in the circuitpoint in the circuit
 It can also have a low amount ofIt can also have a low amount of
potential energy at another pointpotential energy at another point
 The difference in potential energyThe difference in potential energy
between the two points is known asbetween the two points is known as
voltagevoltage

45. What is Voltage?What is Voltage?
 SI unit for voltage is volt (V)SI unit for voltage is volt (V)

46. Measuring VoltageMeasuring Voltage
 VoltmeterVoltmeter

47. VoltmeterVoltmeter
 Connected in parallel acrossConnected in parallel across
the cellthe cell
 Has positive (red) terminal andHas positive (red) terminal and
a negative (black) terminal likea negative (black) terminal like
ammeterammeter
 Positive terminal connected toPositive terminal connected to
the positive side of the cellthe positive side of the cell
 Negative terminal connected toNegative terminal connected to
the negative side of the cellthe negative side of the cell

48. Measuring VoltageMeasuring Voltage
 VoltmeterVoltmeter

49. Different voltage forDifferent voltage for
different electric sourcesdifferent electric sources
 Different electric cell haveDifferent electric cell have
different voltagedifferent voltage
 In Singapore the main voltageIn Singapore the main voltage
is 230Vis 230V
1.5V
9V
12V

50. How are electric cells connectedHow are electric cells connected
in electrical appliances?in electrical appliances?
 Electric cells are connected inElectric cells are connected in
series with the positiveseries with the positive
terminal of one cell touchingterminal of one cell touching
the negative terminal of thethe negative terminal of the
next cellnext cell
 The total voltage across all theThe total voltage across all the
electric cells is equal to theelectric cells is equal to the
sum of the voltages of thesum of the voltages of the
individual cellsindividual cells

51. How are electric cells connectedHow are electric cells connected
in electrical appliances?in electrical appliances?
 For example you have electricFor 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 electricYou will need six 1.5V electric
cellscells

52. CheckpointCheckpoint
Page 63Page 63

53. ObjectivesObjectives
 At the end of this lesson youAt 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 ofUnderstand the different types of
resistorsresistors
 Understand how resistors isUnderstand how resistors is
placed in series and parallelplaced in series and parallel
arrangementsarrangements

54. What is a resistor?What is a resistor?
 Appliances need to ensure thatAppliances need to ensure that
the correct size of current flowsthe correct size of current flows
to operate properlyto operate properly
 To control the size of theTo control the size of the
current, electrical componentscurrent, electrical components
called resistors are used in thecalled resistors are used in the
circuitscircuits

55. ResistorsResistors
AsknLearnAsknLearn

56. Types of resistorsTypes of resistors
 FixedFixed
 VariableVariable

57. Fixed ResistorsFixed Resistors
 One fixed resistanceOne fixed resistance
 Resistance can be a fraction ofResistance can be a fraction of
an ohm to thousands of ohmsan ohm to thousands of ohms
 SI unit is ohmsSI unit is ohms

58. Variable ResistorsVariable Resistors
 Known as rheostatKnown as rheostat
 Vary the resistance in a circuitVary the resistance in a circuit
 Resistance change, the currentResistance change, the current
also changesalso changes
 When resistance decreases,When resistance decreases,
the current increasesthe current increases

59. RheostatsRheostats
 Different types for differentDifferent types for different
purposespurposes

60. Fixed and VariableFixed and Variable
ResistorResistor
AsknLearnAsknLearn

61. Arrangement of resistorsArrangement of resistors
 Can be in series or parallelCan be in series or parallel
 SeriesSeries
 Same current from the electricSame current from the electric
cell passes through each resistorcell passes through each resistor
 As more resistors are added, theAs more resistors are added, the
resistance to flow electricalresistance to flow electrical
charges increasescharges increases
 The current in the circuitThe current in the circuit
decreasesdecreases
 Overall resistance in seriesOverall resistance in series
circuit increasescircuit increases

62. Arrangement of resistorsArrangement of resistors
 ParallelParallel
 For resistors in parallel, currentFor resistors in parallel, current
from the electric cell dividedfrom the electric cell divided
among the resistoramong the resistor
 More resistors added moreMore resistors added more
electrical charges are able toelectrical charges are able to
flow through the resistors at theflow through the resistors at the
same timesame time
 Current in circuit increasesCurrent in circuit increases
 Overall resistance of the parallelOverall resistance of the parallel
circuit decreasescircuit decreases

63. Metal with…Metal with…
 Low resistanceLow resistance
 Copper and silverCopper and silver
 High resistanceHigh resistance
 NichromeNichrome

64. Resistor – Series andResistor – Series and
ParallelParallel
AsknLearnAsknLearn

65. CheckpointCheckpoint
Page 67Page 67

66. ObjectivesObjectives
 At the end of this lesson, youAt the end of this lesson, you
will be able to:will be able to:
 State the heating effects andState the heating effects and
examplesexamples
 Understand what isUnderstand what is
electromagnets and its useselectromagnets and its uses
 Understand what is chemicalUnderstand what is chemical
effects and electroplatingeffects and electroplating

67. Effects of Electric CurrentEffects of Electric Current
 Heating effectHeating effect
 Magnetic effectMagnetic effect
 Chemical effectChemical effect

68. Heating EffectHeating Effect
 Resistance in circuit wiresResistance in circuit wires
affects the amount of electricaffects the amount of electric
current flowingcurrent flowing
 Electric current flows throughElectric current flows through
the wire, the wire gets heatedthe wire, the wire gets heated
upup
 Electrical energy to heatElectrical energy to heat
energyenergy

69. Heating EffectHeating Effect
 Heating element in anHeating element in an
electrical appliance consists ofelectrical appliance consists of
high resistance wires such ashigh resistance wires such as
nichromenichrome
 Very hotVery hot
 Produce more heatProduce more heat
 Connecting wires are made ofConnecting wires are made of
low resistance materials suchlow resistance materials such
as copperas copper
 Less hotLess hot
 Produce less heatProduce less heat

70. Heating EffectHeating Effect
 If resistance wire gets very hot,If resistance wire gets very hot,
light can also be producedlight can also be produced
 Example: Filament of anExample: Filament of an
electric light bulbelectric light bulb

71. Magnetic EffectMagnetic Effect
 Electric current also producesElectric current also produces
magnetic effectmagnetic effect
 Example: placing wire nearExample: placing wire near
compass needle and letcompass needle and let
electric current flow, the needleelectric current flow, the needle
will movewill move

72. Magnetic EffectMagnetic Effect
 ElectromagnetElectromagnet
 Coil of wire usually woundCoil of wire usually wound
around a piece of ironaround a piece of iron
 When current flows, it acts like aWhen current flows, it acts like a
bar magnetbar magnet
 If no current flow, theIf no current flow, the
electromagnet loses itselectromagnet loses its
magnetismmagnetism

73. Magnetic EffectMagnetic Effect
 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 ofIncrease the number of turns of
wire in the coilwire in the coil
 Winding the coil around an ironWinding the coil around an iron
corecore

74. Magnetic EffectMagnetic Effect
 ElectromagnetElectromagnet
 UsesUses
 Magnetic cranesMagnetic cranes
 Electric bellsElectric bells
 Electric motorsElectric motors

75. Chemical EffectChemical Effect
 ElectrolysisElectrolysis
 UsesUses
 ElectroplatingElectroplating
 Extraction of some metalsExtraction of some metals

76. ElectroplatingElectroplating
Watch videoWatch video

77. Chemical EffectChemical Effect
 Extraction of metalsExtraction of metals
 Solid compound of the metal isSolid compound of the metal is
heated until it meltsheated until it melts
 An electric current is thenAn electric current is then
passed through the moltenpassed through the molten
compoundcompound
 Molten compound break down toMolten compound break down to
give the metalgive the metal

78. Do CheckpointDo Checkpoint
Page 72Page 72