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AAA - PHYSICS - Revision > Topic 2-Electricity > Flashcards

Topic 2-Electricity Flashcards

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1
Q

What is an electric current?

A

A flow of charge.

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2
Q

What is the unit of current?

A

Ampere.

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3
Q

If it is a single closed circuit what is the current like?

A

It is the same everywhere in the circuit.

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4
Q

What is the potential difference?

A

The driving unit which pushes the charge around.

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5
Q

What is the unit of potential difference?

A

Volts.

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6
Q

What is resistance?

A

Anything that slows the force down.

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7
Q

What is resistance measured in?

A

Ohms.

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8
Q

What is the relationship between resistance and current?

A

The greater the resistance ,the smaller the current that flows.

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9
Q

How do you work out charge flow?

A

Charge flow=current x time

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10
Q

How do you work out potential difference?

A

Potential difference=Current x resistance.

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11
Q

What does an ammeter measure?

A

The current.

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12
Q

What does the voltmeter measure?

A

Potential difference.

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13
Q

For diodes what does the resistance depend on?

A

The direction of the current.

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14
Q

Does the resistance of an rhombic conductor change?

A

No.

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15
Q

What does LDR stand for?

A

Light dependent resistor.

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16
Q

What is an LDR dependent on?

A

The light intensity.

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17
Q

For an LDR in a bright light what happens to the resistance?

A

It falls.

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18
Q

For an LDR in darkness what happens to the resistance?

A

It is at its highest.

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19
Q

What are LDRs used for?

A

Burglar detectors and automatic night lights.

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20
Q

What is a thermistor dependent on?

A

Temperature.

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21
Q

In hot conditions what happens to the resistance of a thermistor?

A

It drops.

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22
Q

In cool conditions what happens to the resistance of a thermistor?

A

It goes up.

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23
Q

What can thermistors be used for?

A

Car engine temperature detectors and electronic thermostats.

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24
Q

What can sensing circuits be used for?

A

To turn on or increase the power to the components depending off the conditions they are in.

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25
Q

In series circuits is the current shared equally through all components or is it the same current as the total?

A

The same current as the total.

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26
Q

In series circuits is the potential difference shared?

A

Yes.

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27
Q

If you remove a component in a parallel circuit will it most likely affect the other components?

A

No.

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28
Q

If you add a resistor to a parallel circuit what happens to the resistance?

A

It reduces it.

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29
Q

What two types of electricity supplies are there?

A

Alternating current and direct current.

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30
Q

What is the current like in an alternating current supply?

A

It constantly changes direction.

31
Q

How are alternating currents produced?

A

By alternating voltages in which the positive and negative ends keep changing.

32
Q

What energy source do they use in the UK?

A

An ac supply of 230 volts.

33
Q

What does ac stand for?

A

Alternating current.

34
Q

What’s the frequency of the ac mains supply?

A

50 cycles per seconds or 50 hertz.

35
Q

What is direct current?

A

Current that’s always flowing in the same direction.

36
Q

How is direct current created?

A

By direct voltage.

37
Q

How many types of wires are there usually in electrical appliances?

A

3.

38
Q

What are the three types of wires?

A
  • Neutral wire.
  • Live wire.
  • Earth wire.
39
Q

What colour is the neutral wire?

A

Blue.

40
Q

What colour is the earth wire?

A

Green and yellow.

41
Q

What colour is the live wire?

A

Brown.

42
Q

What does the live wire do?

A

It provides alternating potential difference.

43
Q

What does the neutral wire do?

A

It completes the circuit and carries away current.

44
Q

What does the earth wire do?

A

It stops the appliance from becoming live.

45
Q

What happens if you touch a live wire?

A

You will get an electric shock.

46
Q

Why do you get an electric shock if you touch a live wire?

A

Because you body is at 0V which means if you touch a live wire a large potential difference is produced across your body from the current flowing through you.

47
Q

What are the dangers of an electric shock?

A

Death or injury.

48
Q

What does the total energy transferred by an appliance depend on?

A

How long the appliance is on for and it’s power.

49
Q

What is the power of an appliance?

A

The energy it transfers per second.

50
Q

What is the equation for energy transferred?

A

Energy transferred=power x time.

51
Q

What does the power rating tell you on an appliance?

A

It tells you the maximum amount of energy transferred between stores per second when the appliance is in use.

52
Q

How does the power rating affect the cost of the appliance?

A

The lower the power rating the cheaper it is to run.

53
Q

Does a higher power rating mean that it transfers electricity usefully?

A

No.

54
Q

What is the equation for energy transferred?

A

energy transferred=power x time.

55
Q

What is the equation for energy transferred with pd?

A

energy transferred =charge flow x potential difference.

56
Q

What is the equation for power and pd?

A

power=potential difference x current.

57
Q

The higher the battery’s potential difference…

A

The more energy is supplied to the circuit for every coulomb of charge which flows around it.

58
Q

What is the national grid?

A

A system of cables and transformers that covers the UK and connects power stations to consumers.

59
Q

To transmit a large amount of power what do you need?

A

A high potential difference or a high current.

60
Q

What is the problem with a high current in the national grid?

A

You lose lots of energy as the wires heat up and energy is transferred to the thermal energy store of the surroundings.

61
Q

What is an advantage of a high potential difference in the national grid?

A

It’s much cheaper than a high current.

62
Q

Why do materials get static?

A

When materials are rubbed together the negatively charged electrons will be scraped off one and put on to another ,leaving the materials electrically charged.

63
Q

Are both +ve and -ve electrostatic charges only ever produced by the movement of electrons?

A

Yes.

64
Q

What is a positive static charge caused by?

A

Electrons moving elsewhere.

65
Q

As an object gains an electric charge how does this affect the potential difference?

A

It increases.

66
Q

When is a spark formed from static?

A

When the potential difference is large enough to jump across the gap between the object and the earth.

67
Q

Can an electric spark jump to any electric conductor nearby?

A

Yes.

68
Q

Give an example of an electric conductor that a spark can jump to.

A

A human.

69
Q

Opposite charges…

A

Attract.

70
Q

Same charges…

A

Repel.

71
Q

Where is an electric field created?

A

Around any charged object.

72
Q

The closer you get to an object (in terms of field)…

A

The stronger the field strength is.

73
Q

What happens when a charged object is placed in the electric field of another object?

A

It feels a force.(Attraction or repelling)

AAA - PHYSICS - Revision (7 decks)

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