Combined Physics - P2 Electricity Flashcards

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1
Q

What is the circuit symbol for an open switch?

A
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2
Q

What is the circuit symbol for a closed switch?

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3
Q

What is the circuit symbol for a cell?

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4
Q

What is the circuit symbol for a battery?

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5
Q

What is the circuit symbol for a diode?

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6
Q

What is the circuit symbol for a resistor?

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7
Q

What is the circuit symbol for a variable resistor?

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8
Q

What is the circuit symbol for an LED?

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9
Q

What is the circuit symbol for a lamp?

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10
Q

What is the circuit symbol for a fuse?

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11
Q

What is the circuit symbol for a voltmeter?

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12
Q

What is the circuit symbol for an ammeter?

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13
Q

What is the circuit symbol for a thermistor?

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14
Q

What is the circuit symbol for an LDR?

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15
Q

What is current?

A

The rate of flow of charge

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16
Q

What equation links charge flow, current and time?

A

Charge flow = current x time

Q = I t

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17
Q

Describe the IV graph for a resistor at constant temperature.

A
  • Current is directly proportional to potential difference.
  • Resistance is constant.
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18
Q

What type of circuit is shown in the image?

A

Series circuit

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19
Q

Explain the shape of the IV graph for a diode.

A
  • Current only flows in one direction through a diode.
  • There is high resistance in the opposite direction meaning current doesn’t flow.
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20
Q

What equation links potential difference, current and resistance?

A

Potential difference = current x resistance

V = I R

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21
Q

What type of circuit is shown in the image?

A

Parallel circuit

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22
Q

Draw an I-V graph for a filament lamp.

A
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23
Q

For a given potential difference, what happens to the current when the resistance increases?

A

The current decreases.

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24
Q

Explain the shape of the IV graph for a filament lamp.

A

As the current increases the temperature of the filament lamp increases (so the resistance increases) meaning less current can flow per unit potential difference.

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25
Q

Draw an I-V graph for an ohmic resistor (e.g. a resistor at a constant temperature).

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26
Q

Draw an I-V graph for a diode.

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27
Q

What happens to the resistance of a thermistor as temperature increases?

A

Resistance decreases

28
Q

What happens to the resistance of an LDR as light increases?

A

Resistance decreases

29
Q

What’s the difference between direct current and alternating current?

A
  • Direct current flows in only one direction.
  • Alternating current constantly changes direction.
30
Q

What is the rule for current in a series circuit?

A

Current is the same everywhere in the circuit

31
Q

Name the electrical component used in thermostats.

A

Thermistor

32
Q

Where are LDRs commonly found?

A

LDRs are used as automatic night lights / burglar detectors (in bright light the resistance is low)

33
Q

What is the National Grid?

A

A system of cables and transformers

34
Q

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

A

Potential difference is shared between components.

35
Q

Where should you place an ammeter to measure current through a component?

A

The ammeter should be placed in series with the component.

36
Q

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

A

It is the same in each branch.

37
Q

Where should you place a voltmeter to measure potential difference across a component?

A

The voltmeter should be placed parallel to the component.

38
Q

What type of electricity supply is a battery?

A

Direct current (DC)

39
Q

What is the total resistance of the three resistors in series?

A

25 Ω

40
Q

What is the rule for current in a parallel circuit?

A

Current is shared between the branches.

41
Q

What type of electricity supply is mains electricity?

A

Alternating current (AC)

42
Q

Name the equipment used to measure potential difference.

A

Voltmeter

43
Q

What is the frequency of mains electricity?

A

50 Hz

44
Q

Name the three wires in a three-core cable and say what colour they are.

A
  • Live wire (brown)
  • Neutral wire (blue)
  • Earth wire (green / yellow striped)
45
Q

What is the function of the neutral wire (blue)

A

Completes the circuit carrying current away (0 V)

46
Q

What equation links power, current and resistance?

A

Power = current2 x resistance

P = I2 R

47
Q

What is the potential difference of mains electricity?

A

230 V

48
Q

What is the function of the live wire (brown)?

A

Provides the alternating potential difference (230V)

49
Q

What is the function of the Earth wire (green / yellow)?

A

Acts as a safety device, stopping the appliance casing from becoming live (0 V)

50
Q

What equations links power, current and potential difference?

A

Power = current x potential difference

P = I V

51
Q

What two things determine how much energy is transferred by an electrical appliance.

A
  • How long the appliance is on for
  • The power rating of the appliance
52
Q

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

A

Energy transferred = charge flow x potential difference

E = Q V

53
Q

In a parallel circuit, what happens to the total resistance when you add a resistor?

A

The total resistance decreases.

54
Q

Describe how electricity is transmitted across the National Grid to make it as efficient as possible.

A
  • High potential difference
  • Low current
  • Which decreases energy lost by heating the wires/surrounding
55
Q

What equation links energy transferred, power and time?

A

Energy transferred = power x time

E = P t

56
Q

How are step-down transformers used within the National Grid?

A

Step-down transformers bring the 400,000 V of the National Grid down to 230 V for use in the home.

57
Q

Name the equipment used to measure current.

A

Ammeter

58
Q

How are step-up transformers used within the National Grid?

A

Step-up transformers increase the potential difference of the National Grid to 400,000 V

59
Q

Sketch a graph to show resistance against length of wire.

A
60
Q

Sketch a graph to show how light intensity affects resistance in an LDR.

A
61
Q

Sketch a graph to show how temperature affects resistance in a thermistor.

A
62
Q

Sketch a graph to show how the number of resistors affects resistance in a series circuit.

A
63
Q

Describe how you would use the equipment to investigate how the length of wire affects resistance.

A
  • Connect crocodile clips across 10 cm of wire and connect to a power supply.
  • Measure current using ammeter
  • Measure potential difference using voltmeter
  • Calculate resistance using the equation R=V/I
  • Repeat for different lengths of wire (20 cm, 30 cm, 40 cm, 50 cm 60 cm)
64
Q

Describe how you would use the equipment to investigate the relationship between current and potential difference across a resistor.

A
  • Place a variable resistor and ammeter in series with a resistor.
  • Place a voltmeter parallel to the resistor.
  • Measure current using an ammeter.
  • Measure potential difference using a voltmeter.
  • Use the variable resistor to adjust current.
  • Take new readings for current and potential difference.
  • Repeat until you have 5 sets of readings and plot a graph of current (I) against potential difference (V).
65
Q

Describe how to use the following equipment to investigate how adding resistors in series affects total resistance.

A
  1. Take reading off voltmeter for potential difference
  2. Take reading off ammeter for current
  3. Calculate resistance using the equation R=V/I
  4. Add a resistor in series with the first one (in the same loop) and repeat steps 1-3.
  5. Repeat this with up to 5 resistors.
66
Q

Describe how to use the following equipment to investigate how adding resistors in parallel affects total resistance.

A
  1. Take reading off voltmeter for potential difference
  2. Take reading off ammeter for current
  3. Calculate resistance using the equation R=V/I
  4. Add a resistor parallel to the first one (in a separate branch) and repeat steps 1-3.
  5. Repeat this with up to 5 resistors.