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AQA Physics Seperate Science > KO3 Electricity > Flashcards

KO3 Electricity Flashcards

1
Q

What does AC stand for?

A

Alternating current

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2
Q

Define alternating potential difference.

A

Potential difference that repeatedly changes direction across a wire.

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3
Q

What does DC stand for?

A

Direct current

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4
Q

Define direct potential difference.

A

Potential difference that remains in the same direction across a wire.

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5
Q

Is mains electricity AC or DC?

A

AC

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6
Q

Is a battery powered circuit AC or DC?

A

DC

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7
Q

In the context of AC, define frequency.

A

The number of times per second the potential difference changes direction.

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8
Q

State the standard units for frequency.

A

Hertz (Hz)

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9
Q

State the frequency of UK mains electricity.

A

50 Hz

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10
Q

State the potential difference of UK mains electricity.

A

230 V

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11
Q

Name the type of cable used in the UK to connect most common electrical devices to the mains electricity.

A

Three core cable

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12
Q

What colour is the insulation around the live wire?

A

Brown

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13
Q

What colour is the insulation around the neutral wire?

A

Blue

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14
Q

What colour is the insulation around the earth wire?

A

Yellow and green stripes

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15
Q

State the function of the live wire.

A

Carries the alternating potential difference from the supply.

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16
Q

State the function of the neutral wire.

A

Completes the circuit.

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17
Q

State the function of the earth wire.

A

A safety wire to stop appliances becoming live.

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18
Q

State the potential difference between the live and earth wires.

A

230 V

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19
Q

State the potential difference between the live and neutral wires.

A

230 V

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20
Q

In a three core cable, name the wires that should be at 0 V.

A

Earth wire and neutral wire

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21
Q

State when the earth wire will carry a current.

A

When there is a fault.

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22
Q

Explain why not all electronic devices have an earth wire.

A

They do not all have exposed metal that can become live.

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23
Q

In a three core cable, name the wire that is connected to the fuse.

A

Live wire

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24
Q

Explain why the live wire is dangerous even if the switch is not closed.

A

There will be a potential difference across a person if they touch the live wire (person’s feet at 0 V, point of touch at 230 V) which will cause a current to flow through them.

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25
Define power in terms of energy.
Rate of transfer of energy.
26
State the standard units for power.
Watts (W)
27
In words, state the equation that links power, current and potential difference.
power = potential difference × current
28
In symbols, state the equation that links power, current and potential difference.
P = V × I
29
In words, state the equation that links power, current and resistance.
power = (current)² × resistance
30
In symbols, state the equation that links power, current and resistance.
P = I² × R
31
Describe the relationship between the potential difference and power output of a device.
As the potential difference increases, the power output increases.
32
Give two variables that affect the amount of energy transferred by an appliance.
Time the appliance is left on for and its power output
33
Name the store of energy which increases as an electric motor spins faster.
The kinetic energy store of the motor
34
Name the store of energy which increases as the temperature of an electric heater increases.
The thermal energy store of the heater
35
In words, state the equation that links energy transferred, power and time.
energy transferred = power × time
36
In symbols, state the equation that links energy transferred, power and time.
E = P × t
37
In words, state the equation that links energy transferred, charge flow and potential difference.
energy transferred = charge flow × potential difference
38
In symbols, state the equation that links energy transferred, charge flow and potential difference.
E = Q × V
39
If the potential difference across a component is increased, state the effect on the energy transferred.
It increases.
40
If less charge flows through a component, but the potential difference remains the same, state the effect on the energy transferred.
It decreases.
41
If the power rating of a device is higher, state the effect on the energy transferred.
It is transferred more quickly.
42
Describe the components and purpose of the National Grid.
A system of cables and transformers. Links power stations to consumers.
43
State what is transferred across the National Grid.
Electrical power
44
Name the two types of transformers.
Step-up transformer and step-down transformer
45
State the function of transformers.
To alter the potential difference.
46
What does a step-up transformer do to the potential difference?
It increases it.
47
What does a step-down transformer do to the potential difference?
It decreases it.
48
What does a step-up transformer do to the power?
Nothing, the power stays constant.
49
What does a step-down transformer do to the power?
Nothing, the power stays constant.
50
What does a step-up transformer do to the current?
It decreases it.
51
What does a step-down transformer do to the current?
It increases it.
52
Explain why step-up transformers are used to increase the potential difference across transmission cables.
So there is less current in the transmission cables and less energy is lost due to heating.
53
Describe the effect on the efficiency of the National Grid if transformers were not used.
Efficiency would decrease.
54
Describe how insulating materials can be made to be electrically charged.
By rubbing them against one another.
55
Describe how a material can become negatively charged.
By gaining electrons.
56
Describe how a material can become positively charged.
By losing electrons.
57
Describe what occurs when two electrically charged objects are brought close together.
They experience a force (they attract or repel).
58
Two objects have the same electrical charge. Will they attract or repel?
Repel
59
Two objects have opposite electrical charge. Will they attract or repel?
Attract
60
State whether electrostatic force is a contact force or non-contact force.
Non-contact force
61
Explain why there is no potential difference between two insulating objects before they are rubbed together.
They have no charge.
62
Name the event that occurs when a buildup of charge is so large that the charges 'jump' across an insulating gap.
Sparking
63
Name the type of field that surrounds every charged object.
An electric field
64
Where is the electric field strongest around a charged object?
Closest to the object.
65
Describe the relationship between the distance to an electric charge and the strength of the electric field.
As the distance to the electric charge decreases, the strength of the electric field increases.
66
State the direction in which electric field lines point.
Away from positive charges and towards negative charges.
67
Explain which of the diagrams shows the correct electric field lines for a negatively charged object.
A, because the field lines all point towards the negative charge.
68
Explain why a charged object experiences a force when close to another charged object.
Because of the interaction between their electric fields.
69
State how the size of the force between two charged objects can be increased.
By bringing them closer together.
70
State what all non-contact forces have in common.
They all involve fields.

AQA Physics Seperate Science (5 decks)

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