Electricity Flashcards

1
Q

What is an ion?

A

A charged atom

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2
Q

How does charging by friction work?

A

When you rub an insulator, electrons are transferred from one of the materials to the other causing them to become charged.

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3
Q

What type of force do two charged objects exert on each other?

A

non-contact force

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4
Q

Why do two charged objects exert a non-contact force?

A

A charged object has an electric field around itself.

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5
Q

What does each line of force represent?

A

the path that a small positive charge would follow because of the electric field.

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6
Q

If the sphere was negatively charged, what way would the lines of force point?

A

towards the centre of the sphere.

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7
Q

How does sparking occur?

A

When two oppositely charged objects are in close proximity and the electric field around them becomes too strong. This causes some of the electrons to be pulled out of air molecules which then hit other air molecules creating a sudden flow of electrons.

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8
Q

Complete the sentences: Like charges _______. Unlike charges______.

A

repel, attract

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9
Q

What is electric current?

A

The flow of charge/ electrons.

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10
Q

What is used to measure current?

A

ammeter

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11
Q

What is a battery?

A

two or more cells

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12
Q

What is electric charge measured in?

A

coulombs

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13
Q

What is the equation linking charge, time and current?

A

charge = current x time

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14
Q

What is potential difference?

A

The energy transferred by each coulomb of charge that passes a point.

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15
Q

What is the equation linking energy transferred, charge and potential difference?

A

potential difference = energy transferred / time

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16
Q

What is resistance?

A

when atoms resist the passage of electrons through a circuit

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17
Q

What is the equation linking potential difference, resistance and current?

A

V = IR

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18
Q

What is Ohm’s law?

A

The current through a resistor at constant temperature is directly proportional to the potential difference across the resistor.

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19
Q

What is an ohmic conductor?

A

Something that has a constant resistance whilst current changes.

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20
Q

Complete the sentence : The greater the resistance, the _______ steep the line.

A

less

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21
Q

What does reversing the potential diff across a resistor do to the current?

A

reverses it

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22
Q

How can you investigate how the length of a wire affects the resistance? RP

A
  • Set up a series circuit with a cell, switch, ammeter, wire and voltmeter added in parallel.
  • To add the wire tape it to a metre ruler and add crocodile clips 10cm apart.
  • Calculate the resistance of the circuit using R = V/I
  • Repeat by increasing the distance of the crocodile clips by 10cm each time.
  • Record the results
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23
Q

What is a zero error?

A

A reading on a measuring instrument when the value should be zero.

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24
Q

If the temperature of the wire increases, what will happen to the resistance?

A

It will increase

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25
Q

What can you do to reduce the effects of heating when investigating the length of wire on resistance?

A
  • Low potential difference
  • Turn off the current when taking a reading
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26
Q

Draw a current-potential difference graph for a filament lamp.

A

Curved

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27
Q

Draw the current-potential difference graph for a diode.

A

Straight line across x axis then increase in current.

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28
Q

What direction does current flow through a diode?

A

One direction, called the forward direction

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29
Q

What way does the line curve in the forward direction of a diode?

A

towards the y axis

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30
Q

What is a diode?

A

a non-ohmic conductor

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31
Q

In the reverse direction of a diode, what is the current?

A

zero

32
Q

What is an LED?

A

Light-emitting diode

33
Q

What is a thermistor?

A

A temperature dependent resistor

34
Q

What is an LDR?

A

light dependent resistor

35
Q

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

A

decreases

36
Q

What happens to the resistance of an LDR if light intensity increases?

A

decreases

37
Q

In a diode, what is the resistance for the forward and reverse direction?

A

Forward resistance - Low
Reverse resistance - High

38
Q

What is the current like in a series circuit?

A

The same throughout

39
Q

What is the potential difference like in a series circuit?

A

shared between components

40
Q

What is the resistance like in a series circuit?

A

The total resistance is the sum of the resistance of each component

41
Q

What is the current like in a parallel circuit?

A

The total current is the sum of the currents though each of the branches

42
Q

What is the potential difference like in a parallel circuit?

A

The same across each component

43
Q

What is the resistance like of a parallel circuit?

A

The total resistance is less than the least resistant resistor

44
Q

What does every mains circuit have?

A

A live wire and a neutral wire

45
Q

What is current called that only flows in one direction?

A

direct current

46
Q

What is current called that repeatedly reverses its direction?

A

alternating current

47
Q

What is the mains frequency in the UK?

A

50Hz

48
Q

What type of current does the mains electricity have?

A

alternating

49
Q

Where is the neutral wire in a mains circuit earthed?

A

the local electricity substation

50
Q

What supplies electricity to mains appliances?

A

the National Grid

51
Q

What is the National Grid?

A

A network of cables and transformers

52
Q

What are step-up transformers?

A

They increase the alternating potential difference to around 132,000 V so that a lower current is required

53
Q

Where are step up transformers used?

A

Power stations to transfer electricity to the national grid

54
Q

What are step-down transformers?

A

It reduces the voltage of the electricity to supply to consumers from the national grid

55
Q

What voltage are homes and offices in the UK supplied with?

A

230V

56
Q

What do plugs, sockets and cables contain?

A

live wires

57
Q

What is the earth wire?

A

A wire that has 0V and carries a current only if there is a fault.

58
Q

What is the use of the longest pin of a three pin plug?

A

It makes contact with the earth wire of a wall socket circuit so that when it is plugged in, the case is automatically earthed.

59
Q

What are the pins of a plug made from?

A

Brass because it is a good conductor and doesn’t rust. It is harder than copper

60
Q

What is the case material of a plug?

A

An electrical insulator, such as plastic

61
Q

What is a fuse?

A

A component between the live pin and live wire that melts and cuts the live wire off if the current is too high.

62
Q

What coloured wire is the live wire?

A

Brown

63
Q

What coloured wire is the neutral wire?

A

Blue

64
Q

What coloured wire is connected to the earth pin?

A

green and yellow striped

65
Q

What material is used for the wires?

A

copper because it is a good electrical conductor and bends easily

66
Q

What are two-core cables used for?

A

Appliances that have plastic cases

67
Q

What volts are peoples bodies at?

A

0V

68
Q

What is a short circuit?

A

when the live wire touches the neutral wire creating a large current

69
Q

What are mains wires surrounded by?

A

An outer layer of flexible plastic material

70
Q

What is the equation linking power, potential difference and current?

A

Power = current x potential difference

71
Q

What are domestic appliances often fitted with?

A

a 3A, 5A or 13A fuse

72
Q

What is the equation linking current, resistance and power?

A

Power = current^2 x resistance

73
Q

How can you calculate the correct rating for a fuse?

A

electrical power/ potential difference

74
Q

What is the equation linking charge, energy and potential difference?

A

energy = charge flow x pd

75
Q

What does a domestic electricity meter measure?

A

How much energy is supplied