Electricity Practical

Electricity Practical - Transcript

Topic 7 Electricity
Charges Electrons Voltage Current Series Parallel Resistance

The slides are designed to tie in with a set of worksheets but could be adapted or serve as a template for other teachers

Topic 7 page 1
rubbing it with a 4 I charged up a plastic comb by duster pulling it through my hair duster pulling When I put the charged up comb near some foil the foil jumped up to stick to the comb comb

Item Item Plastic comb Plastic ruler Plastic bag Wooden ruler Plastic pen Metal spatula

What it was What rubbed on rubbed hair hair cloth cloth cloth cloth

Topic 7 page 2

Did the bits of Did foil move foil

yes yes yes no yes no

Topic 7 page 3
The electroscope

Stop

Topic 7 page 4
Object Charged Object Plastic comb Plastic rod Plastic bag Plastic ruler Effect on Gold Leaf

Rises up Rises up Rises up Rises up

If an uncharged object is brought near an electroscope the doesn t move gold leaf If a charged object is brought near an electroscope the gold leaf rises up

Topic 7 page 6
Pulling and Pushing
Charged object 1 Charged object 2 What happened

Comb Cling film Cling film Polythene rod Polythene rod Perspex rod

Cling film Cling film Piece of record Polythene rod Perspex rod Perspex rod

Pull together Push apart Pull together Push apart Pull together Push apart

Is there a pattern
Charged object 1

Topic 7 page 6
Charged object 2 What happened

Comb

Cling film different same Cling film Cling film Cling film Piece of record different same Polythene rod Polythene rod Polythene rod different Perspex rod Perspex rod Perspex rod same

Pull together together Push apart apart Pull together together apart Push apart together Pull together Push apart apart

Topic 7 page 6
5 If the charged objects are the same material then they will repel

Topic 7 page 7
Where Does Charge Come From The centre of the atom contains both yellow neutrons and green positive protons

Around the outside are the negative electrons

Topic 7 page 7
1 There are kinds of electrical charge two two called positive and negative 2 a To make an object positively charged remove negative charges you need to b To make an object negatively charged you need to add negative charges 3 If a substance is neutral it means that the negative charges are exactly the balanced by the positive charges balanced

Topic 7 page 8
4 Two charged polythene rods will repel they have the same charge because 5 A cleaned mirror will be dusty within the charge attracts dust 24hrs because 6 A woolen jersey could be attracted to a t nylon shirt because hey would have opposite charges which would attract charges

1 A Van de Graff generator builds up and stores a negative charge stores 2 a Your hair stands on end when you touch a Van de Graff generator your hairs become your because negatively charged and repel each other other b Your hair goes down when you touch a the negative charges water tap because leave you flowing along the pipes to the ground and the hairs stop repelling

Topic 7 page 10

Topic 7 page 11
current When a flows charges are moving


Now fill the blanks blanks

Topic 7 page 12
Battery

Switch Bulb Bulb

A

Ammeter

Topic 7 page 13
Part of circuit Statement Battery measures current Bulb Switch Ammeter pushes the current changes electrical energy to light carries current round circuit

Connecting wire turns the current on and off

Topic 7 page 14
Dim bulb small current Bright bulb large current current

The a bulb the bigger the brighter

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1 a An electric circuit s a path that electricity i can flow along can n b A complete circuit has o gaps allowing electricity to flow along it electricity 0 2A 0 5A 0 65A 5 A B C D 0 95A

Topic 7 page 15
A

A

A

Topic 7 page 15
B A
A

Topic 7 page 15
C
V

V

2a The battery pushes the current through the wires conduct the electricity b The wires c The ammeter measures the current d The switch opens and closes a gap 3a The energy change in the bulb is Electrical energy Light energy b The energy change in the battery is Chemical energy Electrical energy 4a Electricians use symbols to make their diagrams clearer and tidier

Topic 7 page 17

Topic 7 page 18
X Y
0 2

Z

0 2

A

0 2

A

A

Current at X Current at Y Current at Z

0 2 A 0 2 A 0 2 A
atame s all points in

In a series circuit the current is the the circuit

Topic 7 page 19
0 4

Z

A

0 2

A A

X

0 2

Y

Current at X Current at Y Current at Z

0 2 A 0 2 A 0 4 A

In a parallel circuit the current taken from the battery equals sum of the the currents through the two bulbs

Q1 The two bulbs in circuit B make less light than the one bulb in circuit A becauseshares the current B

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between two dim bulbs Q2 No current flows in circuit C because of the bulbs is one blown creating a break in the circuit
Q3 Q4 House lights are better wired in parallel B than series a b dim don t roken

bulb doesn t put whole house into darkness

Using Voltmeters and Ammeters Using Voltmeters and Ammeters
V

Voltmeter connected in parallel

A

Ammeter connected in series series

Correctly Wired
No The voltmeter has been connected in series it should be parallel

V

Correctly Wired

A

No the Ammeter has been connected in parallel it should have been series

Correctly Wired
Yes This Ammeter has been connected correctly in series

A

Correctly Wired
Yes This Ammeter has been connected correctly in series

A

Correctly Wired
V

Yes The Voltmeter has been connected correctly in parallel

Correctly Wired
A

Yes The Ammeter has been connected correctly in series

Effects of Series

As more bulbs are added in series the bulbs grow dimmer

Topic 7 page 23
Circuit Diagram

Conductors

Insulators

Iron Brass Copper Steel Graphite

Plastic Rubber Perspex Glass Wood

Topic 7 page 25
Wire Nichrome copper Tin lead Observation Glows red hot Conducts doesn t get hot Heats up and melts Use Electric fire Conductin g wires Safety fuse

Topic 7 page 26 27
Battery 1 2 3 Battery voltage Bulb brightness

1 5 V 6V 12 V

dim

brighter bright

When the voltage increases the current increases

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5 Write down your ideas The more batteries the brighter the bulb This holds true as long as the batteries face the same way If batteries are reversed they cancel each other out Elephant handout

Topic 7 page 29
Text

Animation 1

Topic 7 page 30
Title Choosing the best type of cable Aim o compare copper nichrome thick thin T long short wires and find the best Method Test thick and thin wires in a circuit and measure how it affects the current using an ammeter Then test copper nichrome and long short wires

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Diagram Results A bulb may be used instead of an ammeter
Current
A

Wire
long short

copper nichrome thick thin

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Conclusion Short wires are better than long wires Copper wires are better than nichrome wires Thick wires are better than thin wires

Topic 7 page 31
Copper has a resistance than nichrome lower Thin wires have resistance than thick ones higher Longer wires have resistance than short ones higher

Topic 7 page 32
The variable resistor

4 Write down what you found out The longer the wire coil the dimmer the bulb the shorter the wire the brighter the bulb

Topic 7 page 33
The variable resistor

Write down what you found out The longer the wire coil the smaller the current and the dimmer the bulb The longer wire has a higher resistance

1 A long thin nichrome wire has a higher thick has a lower resistance because resistance as does copper and short wires 2 a Thick copper wires are good for copper is a carrying current because good conductor and thick wires have low resistance nichrome b Long thin coils of nichrome are used in has a high resistance electric fires because causing it to heat up without melting

Topic 7 page 35

Topic 7 page 35
3 A variable resistor is used to increase and decrease the current by changing the length of a resistance wire 4 When the volume on a radio is turned Down the resistance wire is lengthened

causing a reduction in the current

5 Cookers need thick cabling because they use much

more current than lamps

Topic 7 page 36
The purpose of a fuse is to protect you from a short circuit safety safety Not to make the device work

Circuit Symbols
components used in slides

A

V

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