Electricity

PowerPoint Presentation

ElectricityYear 10GB

SLO

SLODescribe the difference between static electricity and current

Keywords: positive, negative, current, atoms, attraction, repulsion

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Static ElectricityStatic electricity is all around us, it causes:

Sparks as we take off clothing

dust accumulating on TV

a zap when we get out the car

Do not copy, Have you ever heard a crackle when taking off your jumper? This is caused by tiny electric charges on your clothes. It's called static electricity.

Your jumper and shirt get electrically charged as they rub together, and then negative electric charges jump from one to the other. This makes sparks that crackle - you can even see them in a dark room.

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Charges build up as a result of two objects rubbing together (friction, tyres on road, and socks on carpet)

When the charges try to balance out, negative charges jump back to the positive item, an electric current (static electricity) is formed.

Electrons are negatively charged

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Static SnakesCopy this pattern onto tissue paper be careful not to rip the tissue

Cut out along the dotted line, and pull the middle up to make a snake

rub a plastic rod/ruler with the piece of nylon cloth, several times

Wave the rod near (but do not touch) the snakes head.

Can you move the snake without touching it?

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Practical ActivityTaskObservationRepelAttractStrength (high/ med/low)Rub cloth on balloon hold near bran.rub cloth on balloon hold near hair (dry)Rub cloth on balloon hold near running waterRub cloth on rod hold near bran.rub cloth on rod hold near hair (dry)rub cloth on rod hold near running water

ChargesLike charges repel

Unlike charges attract

Electricity1. What is electricity?electricity is a flow of energy2.Where does the energy come from?power supply, socket in wall, energy from burning coal, turning turbines (wind, water, steam)3. What carries the energy?

Electrons flying about the atoms in certain materials.4. Why do electrons move?

They are like magnets, opposites attract, negative electrons move towards a positive terminal.

Electron flowElectricity in wires is a flow of electrons along the wire.What do we call this flow of electrons?Electrical current

What is an electric current?An electric current is a flow of microscopic particles called electrons flowing through wires and components.

+-

In which direction does the current flow? from the Negative terminal to the Positive terminal of a cell.Conventional Current flows from Positive to Negative

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Success CriteriaLabel the following diagrams, (same charge, opposite charge, repel, attract, nothing)

What is the name of the particle which gives the charge to the rods?ElectronsDo static charges move? NODo electrons move in an electric current?YESWhat direction does conventional current flow in?Positive to negative

Complete Scipad page 66-67 What is Electricity

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SLODraw simple circuit diagramsKeywords: components, electrons, positive, negative

http://www.bgfl.org/bgfl/custom/resources_ftp/client_ftp/ks3/science/elecricity_2/electricity.swf

Simple circuits

Here is a simple electric circuit. It has a cell, a lamp and a switch. To make the circuit, these components are connected together with metal connecting wires.cell

lampswitch

wires

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Electric currentWhen electric charges move in a wire, we say that an electric current flows in the wire. It's like the way a current of water flows in a river.

For an electric current to flow, we need two things: something to make the electricity flow, such as a battery or power pack a complete path for the current to flow in. This is called an electric circuit.

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Class simulation using balls, hold ball up over head to signify light bulb going,

have counters of people (current) and balls (energy)

Repeat simulation to show parallel and series18

Circuit diagram

cellswitchlampwires

Scientists usually draw electric circuits using symbols;

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Circuit diagramsIn circuit diagrams components are represented by the following symbols;

cellbatteryswitchlampmotorammetervoltmeterbuzzerresistorvariable resistor

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TaskComplete cut and paste of components, function and symbol

Complete worksheet What bits of a circuit are for.

Complete Scipad pages 68

Drawing CircuitsCircuits should be drawn:With a sharp pencilRuler

Circuits should have:No gapsNo overlapsThe correct symbolsOne symbol on each side

Circuits should be drawn as squares

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TaskDraw the following circuits, put you hand up when you have finished the first one

C

2. Complete Scipad page 69-70

Building CircuitsWhen building circuits:Make sure power is off!Count number of wires neededCount and collect equipment neededStart with power supplySet components out as shown in diagram (In a square and one component per side)Connect with wires

When finished run your finger around circuit diagram and the other hand around circuit, make sure they match and are in the same order.

Put your hand up and get it checked, then turn power on.

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TaskCollect the following gear: set of wires, two lamps, one switch, one ammeter, one power supply

Build each circuit you drew previously, each person in your group needs to have a turn, put your hand up before turning on power supply

Extn: Complete practical and questions on page 221 of Science World 10

Remember red to red and black to black when wiring the ammeter!

Success CriteriaComplete Scipad pages 65-71

What is the name of the particle which carries the charge around the circuit?

Does this particle have a negative or positive charge?

Extn: Circuits are often compared to water flowing in pipes, can you come up with your own analogy for a circuit.

SLODefine conductors and insulators and give examples

Keywords: atom, electrons, insulator, conductor, electron movement

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Practical: Conductors and InsulatorsAim:To find out what materials conduct electricity and which do not, and WHY?

Method:Set up a simple circuit as shown:Set the power supply to 6 VoltsIn the gap put a variety of materials one at a time and record the results in a table.

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Results:

MaterialLight / XConductor or InsulatorRubber BandGlassNailWoodPlasticRubberNichrome wireCabonPaper Clip

Results:

MaterialLight / XConductor or InsulatorRubber BandInsulatorGlassInsulatorNailConductorWoodInsulatorPlasticInsulatorRubberInsulatorNichrome wireConductorCabonConductorPaper ClipConductor

Conclusion:

What types of materials conduct electricity? Why?

metals, have free electrons that can move and pass the electrical current along the substance

What types of materials do not conduct electricity? Why?

- Non metals (plastic, wood, rubber, glass) DO NOT have free electrons that can move and pass on the electrical current

Conductors and Insulators

Success CriteriaComplete Scipad page 72-73

In your own words explain the difference between conductors and insulators.

Extn: Complete Challenges on page 228 Science World 10

SLOUnderstand how current flows in series and parallel circuits

Predict ammeter and voltmeter readings in parallel and series circuits

Keywords: components, electrons, positive, negative, parallel, series

Types of circuitThere are two types of electrical circuits;

SERIES CIRCUITSPARALLEL CIRCUITS

The components are connected one after the other. They make a simple loop for the current to flow round.SERIES CIRCUITS

If one bulb blows it breaks the whole circuit and all the bulbs go out.

PARALLEL CIRCUITS

The current has a choice of routes.The components are connected side by side. If one bulb blows there is still be a complete circuit to the other bulb so it stays alight.

Set up the following circuits and fill in the table below, get your diagrams checked before building the circuit:

Practical: Series and Parallel CircuitsNumber of BulbsSeries or ParallelBrightness of bulbCircuit Diagram1SeriesHigh2Series3SeriesRemove a bulb, what happens?2Parallel3ParallelRemove a bulb what happens?

Removing bulbs, means unscrewing them, not disconnectioning them39

Success CriteriaWhat happens to the brightness of the bulbs as you add more in series? Why?

What happens to the brightness of the bulbs as you add more in parallel? Why?

What happens when you take out a bulb in the series circuit? Why?

What happens when you take out a bulb in the parallel circuit? Why?

Would you wire your house in a parallel or series circuit? Why?

Electric currentWhen electric charges move in a wire, we say that an electric current flows in the wire. It's like the way a current of water flows in a river.

For an electric current to flow, we need two things: something to make the electricity flow, such as a battery or power pack a complete path for the current to flow in. This is called an electric circuit.

Do not copy, reminder about what current is

Class simulation using balls, hold ball up over head to signify light bulb going,

have counters of people (current) and balls (energy)

Repeat simulation to show parallel and series41

Measuring current

Electric current (number of electrons flowing past a point) is measured in amps (A) using an ammeter connected in series in the circuit.A

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Measuring current

AA

This is how we draw an ammeter in a circuit.SERIES CIRCUITPARALLEL CIRCUITWhy do we connect the ammeter into the circuit? Hint what is it counting?

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Practical: Measuring Current in a Series CircuitDraw and then set up the following circuits and record the current below the ammeter in your circuit diagram.(remember red to red, black to black)Power pack + ammeter + light bulb + variable resistor

Power pack + light bulb + ammeter + variable resistor

Power pack + light bulb + variable resistor + ammeter

What do you notice about the current readings? Why do you think it is like this? Complete Scipad pages 76-77

Practical: Measuring Current in a parallel CircuitDraw and then set up the following circuits and record the current below the ammeter in your circuit diagram.(remember red to red, black to black)Power pack + three bulbs in parallel + ammeter in first branchPower pack + three bulbs in parallel + ammeter in second branchPower pack + three bulbs in parallel + ammeter in third branch

What do you notice about the current readings? Why do you think it is like this?

Measuring currentSERIES CIRCUITPARALLEL CIRCUIT current is the same at all points in the circuit.

2A2A2A

current is shared between the componentsCurrent in = current outCurrent on branches adds up to current in

2A2A

1A

1A

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Copy the following circuits, set them up, get them checked and fill in the missing ammeter readings.

??4A

4A4A

3A?

?

1A

?3A1A1APractical: Measuring Current

In an electric c____, current is the flow of e_______. The bigger the current, the m___ electrons are flowing around the circuit. The w___ carry the electrons from one terminal around the circuit to the other t______.Current

lampsircuitlectronsoreireserminal

Set up the two circuits shown:In which circuit are the bulbs the brightest?In circuit A the bulbs are the brightest.What happens if you unscrew one bulb in Circuit A?The other bulb stays lit.What happens if you unscrew a bulb in circuit B?The other bulb goes out.What do we call circuit A?Parallel CircuitWhat do we call circuit B?Series CircuitBRIGHTERDIMMER

A.B.

Measuring current ISet up the circuit shown belowand then record the current using an ammeter in the places shown below.What do you notice about the readings?The current is the same for each ammeter.In a series circuit the current is the same wherever you measure it. When measuring current ammeters are always placed in series.

A

A

A

Measuring current IISet up the circuit shown belowthen record the current at the locations shown.What do you notice about the readings?For a parallel circuit, the current that leaves the cell or battery is the same as the current that returns to the cell or battery. The current does not get used up by a circuit, just the energy the electrons are carrying. A1 = A4The sum of the currents in the branches of a parallel circuit is the equal to the current that leaves the cell or battery. A1 = A2 + A3 =A4AmmeterCurrent(A)A1A2A3A4

0.80.80.40.4

A1

A2

A3

A4


SLOKeywords: components, electrons, positive, negative, parallel, seriesUnderstand how current flows in series and parallel circuits

Predict ammeter and voltmeter readings in parallel and series circuits

Measuring voltage

V

This is how we draw a voltmeter in a circuit.SERIES CIRCUITPARALLEL CIRCUIT

V

Why do we put it in parallel and not series?54

Measuring voltageThe electrical push which the cell gives to the current is called the voltage. It is measured in volts (V) on a voltmeter

V

Series circuit

1.5V voltage is shared between the components

1.5V

3V

Set up the following circuit and measure and record the voltage readings

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voltage is the same in all parts of the circuit.

3V

Parallel circuit

3V

3V

Set up the following circuit and measure and record the voltage readings

V

Measuring voltage

V

V

V

The v_____ is a measure of how big a push the e_______ are given as they leave the cell or b_____. The bigger the voltage, the bigger the p___. The cell, battery or p____ s_____ produces the voltage.Voltage

lampsoltagelectronsatteryushower upply

Measuring voltage I

V2

V3

V1

Set up the apparatus as shownthen record the voltages at the locations shown.What do you notice about the readings?For a series circuit, the sum of the voltages for each component is equal to the voltage across the cell or battery.V1 = V2 + V3NB Voltmeters are connected in parallelVoltmeterVoltage(V)V1V2V3

1.50.750.75

Series circuit

Measuring voltage II

V1

V2

V3VoltmeterVoltage(V)V1V2V3

1.51.51.5

Set up the apparatus as shown...measure the voltage at the locations shown.What do you notice about your readings?For a parallel circuit, the voltage across the cell/battery is the same as the voltage across each branch.V1 = V2 = V3


Complete worksheets provided

Complete Test Yourself on page 236-237 Science World 10

Copy the main ideas on page 236. Extn: Make notes into a mind map, poster, who has I have game.

SLOKeywords: attract, repel, poles, magnetic field, like, unlike, electromagnets,

N

SThe iron filings feel the effect of the magnetic field and show the direction of the forces in this region.The region around a magnet where it has a magnetic effect is called its magnetic field.

When a magnetic material is placed in a magnetic field it will experience a force. What is a magnetic field?

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weakest field further away from poles

What is the shape and direction of the lines of force in the magnetic field around a bar magnet?

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S Shape of a magnetic fieldWhere is the magnetic field strongest?Complete scipad page 84 on Magnetism

strongest field at polesstrongest field at poles

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N

N

S

S Magnetic field pattern: N poles togetherWhat do you notice about the pattern of the lines of force in the region between the two north poles?

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NNHow does this pattern compare with the pattern between the two north poles? Magnetic field pattern: N and S poles togetherWhat do you notice about the pattern of the lines of force in the region between the north and south poles?

S

S

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Magnetic Fields- Opposite poles touching

- Like poles touching

Maglev

The Earths Magnetic FieldUsed to protect us from UV radiationUsed in navigation pigeons, whales and humans (compass)

Forces between magnets experiment

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Success CriteriaComplete Scipad pages 84-91 on MagnetismComplete scipad page on Maglev

List the advantages and disadvantages of maglev

How are magnetic fields used by living things?

Draw the magnetic field of two North poles coming togetherDraw the magnetic field of a North and South pole coming togetherDraw the magnetic field of a single magnet

Revisionhttp://www.bbc.co.uk/schools/ks3bitesize/science/energy_electricity_forces/electric_current_voltage/activity.shtml

Electricity

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