Introducing electricity-1282368962-phpapp01
Transcript of Introducing electricity-1282368962-phpapp01
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
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
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
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
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 to the light bulb and back to the other end of the cellthe other 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
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
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
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
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
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
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 series with the positive terminal of one cell touching terminal of one cell touching the negative terminal of the the negative terminal of the next cellnext cell
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
ObjectivesObjectives
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
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
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
ObjectivesObjectives
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 EffectHeating Effect
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
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 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
Magnetic EffectMagnetic Effect
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
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 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
Magnetic EffectMagnetic Effect
ElectromagnetElectromagnet UsesUses
Magnetic cranesMagnetic cranes Electric bellsElectric bells Electric motorsElectric motors
Chemical EffectChemical Effect
ElectrolysisElectrolysis UsesUses
ElectroplatingElectroplating Extraction of some metalsExtraction of some metals
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