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GCSE AQA COMBINED SCIENCE PHYS P1 > P2 ELECTRICITY > Flashcards

P2 ELECTRICITY Flashcards

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1
Q

what can be said about the value of current at any point in a single closed loop?

A

current is the same at all points in a closed loops

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2
Q

2 factors that current in a circuit depend on?

A

potential difference
resistance

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3
Q

define electrical current

A

the rate of flow of electrical charge

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4
Q

define an ohmic conductor?

A

a conductor where resistance remains constant as the current changes.

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5
Q

name four non-ohmic conductors?

A

lamps , diodes , thermistor , LDRs

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6
Q

name two ohmic conductors?

A

wires , fixed , resistors

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7
Q

describe how the resistance of a filament lamp changes with temperature?

A

as temperature increases , the resistance increases.
ions in metals have more energy , so vibrate more often causing more collisons with electrons as they flow through the metal , creating greater resistance to current flow

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8
Q

describe how a diode conducts electricity

A

it only conducts electricity in one direction as it has a very high pressure in the backwards direction

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9
Q

describe how the resistance of a thermistor changes with temperature ?

A

as temperature increases , the resistance decreases.

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10
Q

describe a use of thermistors

A

thermistors can be used in thermostat circuits to automatically turn the heating on when it gets too cold , or switch it off when its gets hot

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11
Q

describe how the resistance of an LDR changes with light intensity

A

as light intensity increases , the resistances decreases.

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12
Q

describe a use of LDRs

A

can be used in automatic lights , to turn on automatically when it gets dark ,and switch off automatically when it gets light

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13
Q

which two things are needed for charge to flow through a circuit

A

the circuit must be closed and there must be a source of potential difference

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14
Q

state the rule for current in a series circuit?

A

the current will be the same at all points in a series circuit.

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15
Q

if the resistance of a component increases , what will happen to the current through that component?

A

it will decrease

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16
Q

unit for potential difference

A

Volts (V)

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17
Q

units for resistance

A

Ohms (Ω)

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18
Q

describe how current is measured

A

with an ammeter connected in series

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19
Q

describe how voltage is measured

A

with a voltmeter connected in parallel to the component you want to measure

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20
Q

what are the two ways that a component can be connected in a circuit ?

A

series (same loop)
parallel (adjacent loop)

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21
Q

give the rule for current in series current

A

the current is the same at all points in a series current

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22
Q

give the rule for current in parallel current

A

the current in a parallel circuit is shared between the branches of the circuit .

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23
Q

give the rule for resistance in a parallel circuit

A

when resistors are connected in parallel , the total resistance is less than the resistance of the smallest resistor.

24
Q

give the rule for resistance in a series circuit

A

the total resistance in a series circuit is the sum of all the individuals resistances

25
Q

give the rule for potential difference in a series circuit

A

potential difference is shared between the components in a series current

26
Q

give the rule for potential difference in a parallel circuit

A

potential difference is the same in each branch of a parallel circuit

27
Q

describe a series circuit

A

a circuit where all components are connected in one single loops

28
Q

describe a parallel circuit

A

a circuit where there are multiple paths and current could take

29
Q

describe the current in series circuit

A

the current is the same at all positions since the charge only has one path to flow through

30
Q

describe the current in series circuit

A

the current is shared between the different branches . when the charge reaches a junction it splits

31
Q

why is it advantageous to connect lamp in parallel

A

if one lamp blows the rest will be unaffected and can still receive current

32
Q

is mains electricity an a.c supply or d.c supply?
what do these stand for?

A

mains electricty is an a.c supply
a.c = alternating current
d.c = direct current

33
Q

what is alternating current?

A

current that continously changes direction at a specific frequency.

34
Q

what is direct current?

A

one directional current flow

35
Q

what is the frequency and voltage of the UK mains electricity supply?

A

frequency = 50hz
voltage = 230v

36
Q

how many wires are usually in the cables connecting electrical appliances to the main?
name these wires

A

live wire
neutral wire
earth wire

37
Q

state the insulation colour used on the earth wire

A

green and yellow

38
Q

state the insulation colour used on the live wire

A

brown

39
Q

state the insulation colour uses on the neutral wire

A

blue

40
Q

explain when the earth wire does and doesn’t carry a current

A

if there is a fault current will flow to the ground.

under normal circumstances no current flows through the earth wire

41
Q

what potential is the neutral wire at

A

0 volts

42
Q

state the potential difference between the live wire and earth wires

A

230 volts

43
Q

purpose of neutral wire?

A

to complete the circuit by connecting main appliances back to the main supply

44
Q

for metal appliances where is the earth wire connected to?

A

earth wire is connected to the metal casing of the appliance.
if live wire becomes loose and touches the casing, the current will flow through the earth wire , preventing electrocution

45
Q

what 2 main factors does the amount of energy transferred by an appliance depend on?

A

how long the appliance is being used for.
the power of the appliance

46
Q

describe the energy transfers in a battery powered torch?

A

The battery converts chemical energy into electrical energy.
bulb converts electrical energy into light as well as waste energy in the form of heating

47
Q

describe the energy transfer in a battery powered motor?

A

battery converts chemical energy into electrical energy.
motor converts electrical energy into kinetic energy as well as waste energy in the form of heating due to friction

48
Q

3 things that determine the power of the circuit?

A

the p.d across the circuit.
current given through the circuit
amount of energy transferred in a given time

49
Q

purpose of national grid?

A

to link power stations to consumers so that they have access to a source of electricity

50
Q

two types of transformers in national grid?

A

step up
step down

51
Q

where are step up transformers found? and what do they do?

A

used when connecting power stations to transmission cables.

increase potential difference

52
Q

where are step up transformers found? and what do they do?

A

used when connecting power stations to transmission cables.

increase potential difference

53
Q

where are step down transformers found? and what do they do?

A

used connecting transmission cables to domestic buildings

decrease potential difference

54
Q

why do transmission lines transfer electricity at high potentials?

A

high potential , results in a low current
lower the current the less energy is wasted that is wasted as heat

therefore is more efficient

55
Q

why do transmission lines transfer electricity at high potentials?

A

high potential , results in a low current
lower the current the less energy is wasted that is wasted as heat

therefore is more efficient

56
Q

why does the potential need to be decreased between transmission lines and houses

A

lower potentials are safer for domestic use and reduce the likelihood of severe electrocution

appliances are designed for 230v

GCSE AQA COMBINED SCIENCE PHYS P1 (4 decks)

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