P2 Electricity Flashcards

1
Q

battery

A

two or more cells

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2
Q

current

A

measure of the flow of electrons around the circuit

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3
Q

current measured in

A

amps (A)

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4
Q

potential difference is the force driving the flow of

A

electrons

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5
Q

potential difference is provided by the

A

cell/battery

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6
Q

potential difference is measure in

A

Volts (V)

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7
Q

resistance is

A

everything that resists or opposes the flow of electrons around

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8
Q

resistance is measured in

A

Ohms (Ω)

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9
Q

current always flows from

A

positive terminal to negative terminal (even though it makes no sense)

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10
Q

what is ohm’s law

A

v = i x r

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11
Q

so long as resistance remains constant, potential difference and current are…

A

directly proportional

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12
Q

on current/potential difference graphs, the greater the resistance =

A

the less steep the gradient

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13
Q

temperature increase=

A

resistance increase

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14
Q

what does current increase result in on IV characteristics graph

A

current increase = increase heat = increase resistance = gradient less steep

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15
Q

diodes only allow current to flow

A

in one direction

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16
Q

diodes only show current when potential difference is

A

positive

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17
Q

what do diodes have in the opposite direction so that no current can flow?

A

really high resistance

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18
Q

charge is

A

a measure of the total current that flows within a certain period of time

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19
Q

charge is measured in

A

coulombs (C)

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20
Q

what happens if a component breaks in a series circuit?

A

the whole circuit stops working

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21
Q

how is the potential difference shared in a series circuit

A

across all components

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22
Q

in series circuits, Vtotal =

A

V1 + V2 + V3…

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23
Q

How is current shared in series circuits?

A

Current is the same everywhere

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24
Q

Current is measured by an

A

Ammeter

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25
Q

Ammeters are placed

A

in series

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26
Q

why can ammeters be placed anywhere in series circuit

A

because current is the same everywhere

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27
Q

in series circuits, total resistance =

A

sum of resistance of each component

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28
Q

voltage of single component =

A

current x resistance of component

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29
Q

what are volts measured by

A

voltmeter

30
Q

voltmeters are connected in

A

parallel to the component you are looking at

31
Q

components with greater resistance always have

A

a higher share of the voltage

32
Q

parallel circuits are circuits with

A

more than 1 loop

33
Q

in parallel circuits, if a component breaks

A

the overall circuit is still in tact

34
Q

in parallel circuits, the potential difference of components are always the same as the total

A

Vtotal = V1 = V2 = V3

35
Q

in parallel circuits, the sum of each loops current

A

adds to the total current that flows

36
Q

In parallel circuits, Itotal =

A

I1+I2+I3…

37
Q

In parallel circuits, loops that have greater resistance

A

take a lower share of the current

38
Q

electrical current takes the

A

path of least resistance

39
Q

more components in parallel=

A

lower total resistance

40
Q

most power stations generate thermal energy and convert it into

A

electrical energy

41
Q

power stations often run way below maximum capacity in order to

A

cope if demand skyrockets

42
Q

power is measured in

A

Watts (W)

43
Q

why is high current an issue for the transmition of electrical power through the national grid?

A

high current = lots of heat, resulting in a lot of energy lost to thermal store

44
Q

why is voltage so high on the national grid?

A

p = v x i and current has to be really low, so voltage must be really high to still have high power output

45
Q

what do step-up transformers do?

A

increase voltage to 400,000V

46
Q

what do pylons do?

A

transmit electricity across the country

47
Q

what do step-down transformers do?

A

reduce voltage to safe levels before electricity reaches towns and cities

48
Q

what is alternating current (AC)

A

when the direction of current often swaps back and fortn

49
Q

when does alternate current occur?

A

when potential difference fluctuates between positive and negative

50
Q

what current is mains supply

A

alternating current

51
Q

mains supply alternates between…
at a rate of…

A

+230V and -230V at a rate of 50Hz

52
Q

direct current remains

A

either positive or negative the whole time

53
Q

whit direct current, charge is always

A

flowing in the same direction

54
Q

what displays AC and DC graphs on a monitor

A

oscilloscopes

55
Q

what colour is the live wire?

A

brown

56
Q

what colour is neutral wire?

A

blue

57
Q

what colour is earth wire?

A

striped green and yellow

58
Q

what are wires in mains supply made of and why?

A

copper to conduct electricity

59
Q

what must copper wires in mains supply be coated in and why

A

insulating plastic for safety

60
Q

what does the live wire do?

A

provides alternating potential difference of 230V

61
Q

what does neutral wire do?

A

carries away current

62
Q

in terms of the live and neutral wire, what does potential difference do?

A

flows in through live wire and out through neutral wire

63
Q

in the neutral wire, what potential difference is electricity?

A

0V

64
Q

what potential difference does earth wire have?

A

0V

65
Q

what is the purpose of earth wire?

A

safety: if the live wire comes into contact with the appliance casing, the earth wire stops the casing from having a high voltage by providing an alternate pathway for current to flow

66
Q

difference in voltage causes

A

electricity to pass from one to the other

67
Q

electricity passes from

A

high voltage to low voltage

68
Q

why do humans get electrocuted if they touch the live wire?

A

the live wire has a voltage of 230V and humans have a voltage of 0V, electricity moves from high voltage to the low voltage

69
Q

What sort of resistance do conductors have

A

very low resistance

70
Q

total resistance of resistors in parallel

A

is less than the resistance of the smallest resistor

71
Q

mA = milliAmps:

A

divide by 1000 to get Amps

72
Q

MA = megaAmps:

A

times by 1,000,000 to get amps