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A Physics Mock Study pt2 > Electricity - GCSE > Flashcards

Electricity - GCSE Flashcards

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1
Q

what is a current?

A

it is the rate of flow of charge round the circuit

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2
Q

what do electrons usually carry?

A

charge. They are negatively charged particles

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3
Q

where will current only flow through?

A

it will only flow through a component if there is a voltage across that component.

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4
Q

what is current measured in?

A

aperes, A

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5
Q

what is voltage?

A

it is what drives the current round the circuit. Kind of like “electrical pressure”

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6
Q

what could be another name for voltage?

A

potential difference

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7
Q

what is voltage measured in?

A

in volts, V

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8
Q

what is resistance?

A

it is anything in the circuit which slows the flow down

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9
Q

what happens if you add more components to the circuit?

A

there will be a higher resistance

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10
Q

how is there a balance between the voltage, current, and resistance?

A

the voltage is trying to push the current round the circuit, and the resistance is opposing it.

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11
Q

what decides how big a current will be?

A

The relative sizes of the voltage and resistance

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12
Q

what happens if you increase the voltage?

A

more current will flow

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13
Q

what happens if you increase the resistance?

A

the less current will flow (or more voltage will needed to keep the same current flowing)

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14
Q

IMPORTANT TO KNKOW THE CIRCUIT SYMBOLS

A

https://quizizz.com/join/quiz/58fcd24a3635b511003ede9e/start

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15
Q

what does the ammeter do?

A

measures the current flowing through the components

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16
Q

where is the ammeter placed?

A

it must be placed in the series anywhere in the main circuit, but never in a parallel

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17
Q

what does a voltmeter do?

A

it measures the voltage across the component

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18
Q

where is the voltmeter placed?

A

must be placed in parallel around the component under test, NOT around the variable resistor or the battery

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19
Q

what is the circuit used for?

A

testing components

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20
Q

what does it mean when you say that the component, the ammeter and the variable are all in series?

A

it means that they can be put in any order in the main circuit

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21
Q

what happens if you alter the resistance of the variable resistor?

A

the current flowing through the components changes

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22
Q

what does a.c. mean?

A

alternating current, meaning the current is constantly changing direction

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23
Q

what does d.c mean?

A

direct current, meaning the current keeps flowing in the same direction

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24
Q

would a main supply be d.c. or a.c.?

A

a.c. -> alternating current

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25
Q

would cells and batteries be d.c. or a.c.?

A

d.c. -> direct current

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26
Q

what is the formula linking Voltage and Current?

A

voltage = current x resistance

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27
Q

what do current-voltage graphs show?

A

how the current varies as you change the voltage

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28
Q

what happens when a metal filament lamp temperature increases?

A

the resistance increases

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29
Q

the current through a wire (at a constant temperature) is proportional to what?

A

proportional to voltage

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30
Q

the current through a resistor (at a constant temperature) is proportional to what?

A

to voltage

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31
Q

different resistors have different what?

A

different resistances

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32
Q

current will only flow through a diode in what?

A

in one direction

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33
Q

when do light-emitting diodes (LEDs) emit light?

A

it emits light when a current flows through them in the forward direction

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34
Q

what do LEDs have lots of? and what are LEDs used for?

A
  • -> lots of practical applications

- -> used for the number on digital clocks, in traffic lights and in remote controls

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35
Q

what do LEDs do not have? (unlike light bulbs)

A

filament that can burn out

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36
Q

what do LEDs indicate?

A

the presence of current in a circuit

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37
Q

what is a Light-dependent resistors (LDR)?

A

a special type of resistor that changes its resistance depending on how much light falls on it

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38
Q

how does the resistance in LDRs change in bright light?

A

the resistance falls

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39
Q

how does the resistance in LDRs change in darkness?

A

the resistance is highest

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40
Q

what is a thermistor?

A

a temperature-dependent resistor

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41
Q

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

A

the resistance drops

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42
Q

what happens to the resistance of a thermistor in cold conditions?

A

the resistance goes up

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43
Q

LDRs are useful device for what?

A

for various electronic circuits

44
Q

thermistors make useful what?

A

temperature detectors

45
Q

in a series circuit, how are the different circuits connected?

A

in a line, end to end

46
Q

what happens if you remove or disconnect one component of a circuit?

A

the circuit is broken and they all stop working

47
Q

in a series circuit, the total resistance of the circuit depends on what?

A

the number of components and the type of components used

48
Q

how do you calculate the total resistance?

A

it is the sum of the resistance of each component in the circuit.

you just need to add all the resistances up

49
Q

in a series circuit, the total potential difference of the supply is shared between what?

A

between the components

50
Q

in a series circuit, the size of the current depends on what?

A

on the total potential difference and the total resistance of the circuit

51
Q

what are the 2 different types of circuits?

A
  • parallel circuits (everything is independent)

- series circuits (all or nothing)

52
Q

in a parallel circuit, what happens if you disconnect or remove one component?

A

it will hardly affect the others at all

53
Q

how is the potential difference in a parallel circuit?

A

it is the same across all branches

54
Q

what causes the total resistance of the parallel circuit to decrease?

A

if you add a second resistor in the circuit

55
Q

what is the scientific name for saying ‘charge flows’?

A

current

56
Q

what is current?

A

it is the rate of flow of electrical charge around a circuit

57
Q

in solid metal conductors, charge is carried by what?

A

negatively charged electrons

58
Q

charge through a circuit depends on what?

A

current and time

59
Q

what is the formula for charge?

A

charge = current x time

60
Q

how much charge passes around a circuit when a bigger current flows?

A

more charge

61
Q

what happens when an electrical charge goes through a change in voltage?

A

energy is transferred

62
Q

why is energy supplied to the charge at the power source?

A

to raise it through a voltage

63
Q

when does charge give up the energy that was supplied at the power source?

A

when it falls through any voltage drop in components elsewhere in the circuit

64
Q

if the change in a voltage is bigger what will happen?

A

more energy is transferred for a given amount of charge passing through the circuit

65
Q

if more energy is transferred for a given amount of change passing through a circuit, what will happen to a battery with a bigger voltage?

A

it will supply more energy to the circuit for every coulomb of charge which flows round it

66
Q

why will a battery with a bigger voltage supply more energy to the circuit for every coulomb of charge which flows round it?

A

it will supply more energy to the circuit because the charge is raised up higher at the start, meaning more energy will be dissipated in the circuit too

67
Q

what is voltage?

A

it is the energy transferred per unit of charge passed

68
Q

what is one volt equal to?

A

one joule per coulomb

69
Q

what is the formula for energy transferred?

A

energy transferred = charge x voltage

70
Q

what is the formula for calculating the energy transferred by an amount of charge as it passes through a resistance?

A

energy transferred = charge x current x resistance

71
Q

how many wires are there in a plug and what are they?

A

there are 3: live, neutral and earth

72
Q

which of the 3 wires are usually needed?

A

the live and neutral, however if something goes wrong the earth wire stops you from getting hurt

73
Q

what does the live wire do?

A

it alternates between a high positive and negative voltage of about 230 V

74
Q

what V is the neutral wire always at?

A

at 0 V

75
Q

in which wires does electricity normally flow through?

A

live and neutral wire

76
Q

what are 3 things that are used for safety and work together?

A
  • earth wire
  • fuse
  • (sometimes) circuit breaker
77
Q

what do all appliances with metal cases must be done to reduce the danger of electric shock?

A

they must be earthed

78
Q

what does earthing mean?

A

it means that the case (metal case) must be attached to an earth wire

79
Q

what can an earthed conductor never become?

A

it can never become live

80
Q

what is an appliance that has a plastic casing and no metal parts showing said to be?

A

a double insulated

81
Q

what is an insulator?

A

it is a plastic case that stops a current flowing (this means you can’t get a shock)

82
Q

anything with double insulation doesn’t need a what?

A

an earth wire, it just needs a live and neutral

83
Q

what happens if the live wire somehow touches the metal case?
(3 steps)

A

1) Nothing will happen because the metal case is earthed, causing a big current to flow through the live wire, through the case and the earth wire.
2) Then the surge in current melts the fuse which cuts off the live supply.
3) this isolates the whole appliance, making it impossible to get an electric shock from the case. This also prevents the risk of fire caused by the heating effect of a large current

84
Q

what is a circuit breaker?

A

an electrical safety devise used in some circuits. They protect the circuit from damage if too much current flows

85
Q

what happens when a circuit breaker detects a surge in current in a circuit?

A

they break the circuit by opening a switch, making circuit breakers more convenient than fuses (which have to be replaced once they’ve melted)

86
Q

what is one type of circuit breaker?

A

a Residual Current Circuit Breaker (RCCB)

87
Q

what happens if somebody touches the live wire?

A

a current will flow through them to the earth. This means the neutral wire carries less current than the live wire

88
Q

what does the RCCB detect?

A

the difference in a current and cuts of the power by opening a switch

89
Q

why can the RCCB operate much faster than fuses?

A

because they break the circuit as soon as there is a current surge (no time is wasted waiting for the current to melt a fuse. This also makes them safer)

90
Q

why do RCCB’s even work for small current changes that might not be large enough to melt a fuse?

A

because even small currents could be fatal, this means RCCB’s are more effective at protecting against electrocution

91
Q

what happens to resistors when an electric current passes through them?

A

they get hot

92
Q

why do resistors get hot when there is an electric current?

A

there is an energy transfer which heats the resistors

93
Q

explain how a energy transfer is caused in resistors?

A

electrons collide with the ions in the lattice that make up the resistors as they flow through it. This gives the ions energy, which causes them to vibrate and heat up

94
Q

what can the heating effect cause in resistors?

A
  • it can increase the resistor’s resistance - so less current will flow, or a greater voltage will be needed to produce the same current
  • it can cause components in the circuit to melt - this means the circuit will stop working, or not work properly.
95
Q

why do fuses use the effect of heating in resistors?

A

they use it to protect the circuits - they melt and break the circuit if the current gets too high.

96
Q

what is one advantage for the heating effect caused in resistors?

A

it is useful if you want to heat something

97
Q

give an example of the heating effect in resistors:

A

toasters contain a coil of wire with a really high resistance. When a current passes through the coil, its temperature increases so much that it glows and gives off infrared (heat) radiation which cooks the bread

98
Q

what do most electrical appliances come with?

A

with a power rating and a voltage rating

99
Q

what is electrical power?

A

it is the rate at which an appliance transfers energy

100
Q

how much energy does an appliance with a high power rating transfer?

A

a lot of energy in a short time

101
Q

where does the energy an appliance transfer come from?

A

it comes from the current flowing through it. This means that an appliance with a high power rating will draw a large current from the supply.

102
Q

what is power measured in?w

A

watts (W)

103
Q

most electrical goods show what?

A

their power rating and voltage rating

104
Q

what do fuses have?

A

they have current ratings and should be rated as near as possible but just higher than the normal operating current

105
Q

what does energy transfer by appliance depend on?

A

it depends on the power of the appliance and how long it is on for

A Physics Mock Study pt2 (8 decks)

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