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electricity key questions Flashcards

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1
Q

what is needed for charge to flow through a closed circuit?

A

a source of potential difference e.g. a cell

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2
Q

state the units for potential difference

A

volts (V)

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3
Q

name the component used to measure potential difference

A

voltmeter

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4
Q

what is a battery?

A

two or more cells

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5
Q

name three sources of potential difference

A

cell, battery, power pack

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6
Q

define potential difference

A

the work done per unit charge

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7
Q

what must a circuit be in order for charge to flow?

A

closed

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8
Q

how must a voltmeter be connected in a circuit?

A

in parallel across the component

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9
Q

state the units of current

A

amps (A)

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10
Q

name the component used to measure current?

A

ammeter

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11
Q

how must an ammeter be connected in a circuit?

A

in series

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12
Q

define current

A

the rate of flow of charge

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13
Q

state the direction of a convectional current

A

positive to negative

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14
Q

write the equation that links charge current and time

A

charge= current x time

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15
Q

state the units of charge

A

coulomb (C)

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16
Q

define resistance

A

a property of electrical components that opposes the flow of charge

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17
Q

state the units of resistance

A

ohms (Ω)

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18
Q

state ohm’s law

A

current is directly proportional to current at a fixed temperature

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19
Q

what is an ohmic conductor

A

a component that follows ohm’s law

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20
Q

state two examples of an ohmic conductor

A

wire, fixed resistor

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21
Q

state two examples of non-ohmic conductors

A

filament bulb, diode

22
Q

write the equation that links potential difference,current and resistance

A

potential difference = current x resistance

23
Q

what is a series circuit?

A

a circuity where components are in one complete loop

24
Q

what is a parallel circuit?

A

a circuit where the components are in more than one loop (branch)

25
Q

describe how the resistance of a thermistor changes as temperature changes

A

as the temperature increases, the resistance decreases

26
Q

describe how the resistance of an LDR changes as light intensity changes

A

as light intensity increases, resistance decreases

27
Q

what do we know about current in a series circuit?

A

it is the same at every point in the circuit

28
Q

what do we know about potential difference in a series circuit?

A

the total potential difference of the power supply is shared between the components, and is based on their resistance

29
Q

describe how we can calculate the total resistance in a series circuit

A

add them up

30
Q

what do we know about the potential difference on a parallel circuit?

A

same as the power supply

31
Q

what do we know about current in a parallel circuit?

A

the current splits across branches and re-joins to go back to the power supply

32
Q

what do we know about the total resistance in a parallel circuit?

A

it is less than the smallest resistance across a branch

33
Q

describe how we can find out the resistance of a component during a practical

A

Use an ammeter in series to measure the current and use a voltmeter in parallel with the component to measure the potential difference. Then use V=IR to calculate the resistance

34
Q

state the potential difference of mains electricity in the UK

A

230V

35
Q

state the frequency of mains electricity in the UK

A

50Hz

36
Q

what is meant by direct current (D.C)?

A

the flow of charge is in one direction only

37
Q

what is meant by alternating current (A.C)?

A

the flow of charge is continually changing direction at a specific frequency

38
Q

what is direct potential difference?

A

the potential difference is in one direction only

39
Q

state an example of source of direct current

A

a battery

40
Q

state a example of source of alternating current

A

mains supply

41
Q

what is alternating potential difference?

A

the potential difference is continually changing direction

42
Q

name three wires inside a plug

A

live (brown), neutral (blue) and earth (green and yellow stripes)

43
Q

name three safety features in a plug

A

earth wire, fuse, plasticised pin

44
Q

define power

A

the rate of energy transfer

45
Q

write the equation linking power, current and potential difference

A

power = current x potential difference

46
Q

write the equation linking power, current and resistance

A

power = current2 x resistance

47
Q

write the equation linking energy, charge and potential difference?

A

energy transferred = charge flow x potential difference

48
Q

what is the national grid?

A

a system of cables and transformers linking power stations to consumers

49
Q

what does step up transformer do?

A

they increase the potential difference from the power station to the transmission cables e.g. 400 000V

50
Q

what does step down transformer do?

A

they decrease the potential difference for domestic use e.g. 230V

51
Q

describe why a high potential difference used to transfer electrical power on the national grid?

A

this creates a low current which reduces energy losses through heating effects, this increases efficiency

Physics (10 decks)

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