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Physics GCSE > Electric circuits > Flashcards

Electric circuits Flashcards

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1
Q

What is the unit for resistance?

A

Ohms (Ω)

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2
Q

What is a series circuit?

A

A circuit with all components on a single loop only

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3
Q

What equation links energy transferred, charge flow, and potential difference?

A

Energy transferred = charge x potential difference
E = QV

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4
Q

What two things are needed for electric charge to flow in a circuit?

A
  • A source of potential difference
  • a closed circuit
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5
Q

What equation links potential difference, current, and resistance?

A

Potential difference = current x resistance
V = IR

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6
Q

What is the unit of current?

A

Amperes or amps (A)

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7
Q

What is the unit of electric charge?

A

Coulombs (C)

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8
Q

What two measurements need to be made to determine the resistance of a component?

A

The potential difference across the component, and the current through the component

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9
Q

What is the rule for potential difference in a parallel circuit?

A

The potential difference across each branch is the same

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10
Q

What is the rule for current in a series circuit?

A

The current is the same through each component and at each point in the circuit

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11
Q

What is the definition of electric current?

A

The rate of flow of charge

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12
Q

What is the rule for potential difference in a series circuit?

A

The sum of the potential differences across each component is equal to the potential difference of the power supply

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13
Q

What equation links charge flow, current, and time?

A

Charge flow = current x time
Q = It

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14
Q

What is the rule for current in a parallel circuit?

A

The total current through the whole circuit is the sum of the currents through each branch

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15
Q

What is true about the current at any point in a single closed loop?

A

It has the same value at any point

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16
Q

What is a parallel circuit?

A

A circuit with components on multiple loops

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17
Q

Definition of current

A

Rate of flow of charge

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18
Q

How does thickness of material affect resistance?

A

As thickness increases (+ length remains constant) more electrons can flow through the wire, so the current is higher + the resistance is therefore smaller

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19
Q

How does length affect resistance?

A

As the length increases (+ thickness is constant) there are more metal ions along the direction of current flow. This means that more collisions occur, so the resistance has increased

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20
Q

How does temperature affect resistance?

A

As temperature increases, the metal ions vibrate faster and with a greater amplitude. This means that the free electrons are more likely to collide with a metal ion, increasing the resistance.

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21
Q

What is meant by an alternating potential difference?

A

The direction of the potential difference changes

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22
Q

What is the job of the earth wire?

A

A safety feature to stop an appliance becoming live

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23
Q

What is a diode?

A

A device which allows current to flow in one direction only

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24
Q

What is the rule for current in a parallel circuit?

A

The total current through the whole circuit is the sum of the currents through each branch

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25
Q

For a given potential difference across a component, if the resistance increases what happens to the current?

A

It decreases

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26
Q

What is the job of the live wire?

A

Carries the alternating potential difference from the supply

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27
Q

Why does a diode only allow current to flow in one direction?

A

It has a very high resistance in the reverse direction

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28
Q

What colour is the insulation on a live wire?

A

Brown

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29
Q

Which wire has green and yellow striped insulation?

A

Earth

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30
Q

What two measurements need to be made to determine the resistance of a component?

A

The potential difference across the component, and the current through the component

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31
Q

Which wire has brown insulation?

A

Live

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32
Q

What is the potential of the live wire?

A

230 V

33
Q

What two things are needed for electric charge to flow in a circuit?

A

A source of potential difference, a closed circuit

34
Q

How does the resistance of an LDR vary with light intensity?

A

Resistance decreases as light intensity increases

35
Q

What equation links power transferred, current, and resistance?

A

Power = (current)^2 x resistance
P = I^2 R

36
Q

What is the potential of the neutral wire?

A

0 V

37
Q

What happens to the resistance of a light bulb as the potential difference increases?

A

The resistance increases

38
Q

How do you calculate the total resistance of a circuit?

A

Total resistance = potential difference across battery / current through battery

39
Q

What is the definition of electric current?

A

The rate of flow of charge

40
Q

What is a parallel circuit?

A

A circuit with components on multiple loops

41
Q

What is the unit of electric charge?

A

Coulombs (C)

42
Q

How does the resistance of a thermistor vary with temperature?

A

Resistance decreases as temperature increases

43
Q

What is the rule for potential difference in a series circuit?

A

The sum of the potential differences across each component is equal to the potential difference of the power supply

44
Q

What is the potential of the earth wire?

A

0 V

45
Q

What is an ohmic conductor?

A

One where the current is directly proportional to the potential difference, meaning the resistance remains constant

46
Q

What equation links energy transferred, charge flow, and potential difference?

A

Energy transferred = charge x potential difference
E = QV

47
Q

Why it is dangerous to provide any connection between the live wire and earth?

A

A large current will flow. If this passes through a person, they will be electrocuted.
They can suffer severe burns and their heart can stop

48
Q

What is the rule for current in a series circuit?

A

The current is the same through each component and at each point in the circuit

49
Q

What colour is the insulation on the earth wire?

A

Yellow and green stripes

50
Q

What equation links potential difference, current, and resistance?

A

Potential difference = current x resistance
V = IR

51
Q

What is the rule for potential difference in a parallel circuit?

A

The potential difference across each branch is the same

52
Q

What is meant by a direct potential difference?

A

The direction of the potential difference is constant

53
Q

What is the National Grid?

A

A system of cables and transformers linking power stations to consumers

54
Q

What is the rule for total resistance in a parallel circuit?

A

The total resistance is less than the resistance of the smallest individual resistor

55
Q

What equation links power transferred, current, and potential difference?

A

Power = current x potential difference
P = IV

56
Q

What colour is the insulation on a neutral wire?

A

Blue

57
Q

What is the job of the neutral wire?

A

Completes the circuit and returns to the power station

58
Q

How does an earth wire stop an appliance becoming live?

A

If a fault occurs, a large current is drawn, which melts the fuse and disconnects the appliance from the mains

59
Q

What is meant by an alternating current?

A

The charges oscillate

60
Q

Which wire has blue insulation?

A

Neutral

61
Q

Where should a fuse be placed in a plug?

A

By the pin for the live wire

62
Q

What is the unit for current?

A

Amperes or amps (A)

63
Q

What is the unit for resistance?

A

Ohms (Ω)

64
Q

What is true about the current at any point in a single closed loop?

A

It has the same value at any point

65
Q

Why does the resistance of a light bulb increase as the potential difference increases?

A

The current increases the temperature of the filament. Free electrons collide with the metal ions, making them vibrate with a greater amplitude

66
Q

Why are step down transformers used on the national grid?

A

To reduce the potential difference to safer values for consumers

67
Q

Why does the total resistance increase when a resistor is added in series?

A

The battery potential difference is now shared across another resistor, meaning the current in the circuit is reduced

68
Q

What is the frequency of the UK mains electricity?

A

50 Hz

69
Q

What equation links charge flow, current, and time?

A

Charge flow = current x time
Q = It

70
Q

Why does the total resistance decrease when a resistor is added in parallel?

A

The potential difference across each resistor is the same, meaning there is another path for current, meaning the current in the circuit increases

70
Q

What is meant by a direct current?

A

The charges flow in a single direction

70
Q

What is the rule for two resistors in series?

A

The total resistance is the sum of the resistance of each resistor
RT = R1 + R2

71
Q

What is a series circuit?

A

A circuit with all components on a single loop only

72
Q

Why can a live wire be dangerous even when a switch in the mains circuit is open?

A

The live wire is still at 230 V if plugged in. If the insulation is damaged and the live wire is exposed, someone touching the wire will provide a connection to earth and they can be electrocuted

73
Q

How can a thermistor be used in a sensing circuit?

A

Put it in series with a fixed resistor and a source of potential difference

74
Q

What is the potential difference of the UK mains electricity?

A

230V

75
Q

The resistance of a piece of wire with a constant thickness is ___ ___ to the length of the wire if the temperature remains constant

A

directly proportional

76
Q

Why are step up transformers used on the national grid?

A

Stepping up the potential difference decreases the current in the transmission cables, decreasing the rate at which the cables are heated by current and increasing efficiency

Physics GCSE (10 decks)

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