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Physics > P2/Electricity > Flashcards

P2/Electricity Flashcards

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1
Q

describe resistance in a thermistor?

A

as temperature increases resistance decreases

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2
Q

where might a thermistor be used?

A

central heating system

oven

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3
Q

describe resistance in an LDR?

A

as light intensity increases resistance decreases

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4
Q

where might an LDR be used?

A

security lighting

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5
Q

describe current in a series circuit

A

it is the same current all the way round

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6
Q

describe potential difference in a series circuit

A

the total potential difference of the power supply is shared between the components

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7
Q

describe total resistance in a series circuit

A

the total resistance of the two components is the sum of the resistance of each component

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8
Q

what is the unit for resistance?

A

Ohm

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9
Q

what is the unit for potential difference?

A

volts

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10
Q

what is the unit for current?

A

amps

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11
Q

describe current in a parallel circuit

A

the total current through the whole circuit is the sum of the currents through the separate components

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12
Q

describe potential difference in a parallel circuit

A

it is the same across each component

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13
Q

describe total resistance in a parallel circuit

A

the total resistance of two resistors is less than the resistance of the separate components

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14
Q

what is the frequency of the UK mains supply?

A

50 Hertz

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15
Q

what is the potential difference of the UK mains supply?

A

230 volts

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16
Q

mains electricity is an a.c supply.

what does this mean?

A

current constant;y changes direction

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17
Q

what does d.c mean?

A

current flows in only one direction

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18
Q

what is needed for electrical charge to flow?

A

a potential difference

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19
Q

what is electric current?

A

a flow of charge

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20
Q

what determines the size of an electrical current?

A

the rate of flow of electrical charge

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21
Q

describe the current in a series circuit

A

it is the same all the way around

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22
Q

what does current through a component depend upon?

A

the resistance of the component and the potential difference across it

23
Q

how does resistance affect current?

A

the higher the resistance the lower the current

24
Q

describe the current through an ohmic conductor

A

current is directly proportional to the potential difference

25
Q

describe the resistance of an ohmic conductor

A

resistance remains constant

26
Q

describe the resistance of a filament lamp

A

the resistance of a filament lamp increases as the temperature of the filament increases

27
Q

describe current flow through a diode

A

current flows in one direction

28
Q

describe resistance of a diode

A

very high resistance in one direction

29
Q

what colour is the live wire?

A

brown

30
Q

what colour is the neutral wire?

A

blue

31
Q

what colour is the earth wire?

A

green and yellow stripes

32
Q

what is the function of the live wire?

A

it carries the alternating potential difference

33
Q

what is the function of the neutral wire?

A

completes the circuit

34
Q

what is the function of the earth wire?

A

it is a safety wire to stop the appliance becoming live

35
Q

what is the potential difference between the live wire and the earth?

A

230v

36
Q

when would the earth wire carry a current?

A

only if there is a fault with the appliance

37
Q

how do electric shocks occur?

A

when a person makes a connection between the live wire (230v) and the earth (0v)

38
Q

what is the unit for power?

A

watt

39
Q

what determines the energy an appliance transfers?

A

its power rating and the length of time it is switched on for

40
Q

in an electrical circuit- work is done when…

A

charge flows in a circuit

41
Q

what is the national grid?

A

a system of cables and transformers linking power station to the cables

42
Q

what do step up transformers do?

A

increase potential difference from the power station to the cables

43
Q

what do step down transformers do?

A

decrease potential difference

44
Q

why do we use transformers in the national grid?

A

to reduce energy loss during transmission by using a high potential difference and low current

45
Q

how do objects become charged?

A

by rubbing two insulators together

46
Q

why do objects become charged?

A

because they gain or lose electrons

47
Q

what is the charge of a material that gains electrons?

A

negative

48
Q

what is the charge of a material that loses electrons

A

positive

49
Q

two objects that carry the same charge will ……. each other

A

repel

50
Q

two objects that carry opposite charge will ……. each other

A

attract

51
Q

is electrostatic force a contact or non-contact force?

A

non-contact

52
Q

what can be found around a charged object?

A

an electric field

53
Q

where is the field strongest?

A

nearest the charged object

Physics (8 decks)

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