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electricity Flashcards

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1
Q

current in a series circuit?

A

the same everywhere

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2
Q

current in a parallel circuit?

A

conserved at a junction in a circuit

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3
Q

voltage in a series circuit?

A

shared between the components

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4
Q

voltage in a parallel circuit?

A

the same on each branch

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5
Q

what is current?

A

the rate of flow of charge

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6
Q

equation for charge?

A

charge = current x time

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7
Q

units for charge equation?

A

charge - Coulomb (C)
current - Amps (A)
time - Seconds (s)

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8
Q

what is voltage?

A

the energy difference of a charge between two points

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9
Q

what is the equation to find energy transferred?

A

energy transferred = charge moved x voltage

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10
Q

what are the units for the energy transferred equation?

A

energy - Joule (J)
charge - Coulomb (C)
voltage - Volt (V)

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11
Q

current is the flow of ………..

A

electrons

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12
Q

what does an ammeter measure?

A

current (in amps)

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13
Q

what does a voltmeter measure?

A

voltage (in volts)

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14
Q

what is another name for voltage?

A

potential difference

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15
Q

what is resistance a measure of?

A

how much a component tries to stop current passing through it

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16
Q

when resistance increases, current ………

A

decreases

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17
Q

what is variable resistor used for in a circuit?

A

to vary the current

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18
Q

what is the equation to work out voltage?

A

voltage = current x resistance

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19
Q

what are the units for the voltage equation?

A

voltage - Volts (V)
current - Amps (A)
resistance - Ohms (Ω)

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20
Q

as voltage increases, current ……

A

increases

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21
Q

resistors in series?

A

when resistors are in series, the total resistance of the circuit is increased because the pathway becomes harder for current to flow through

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22
Q

resistors in parallel?

A

when resistors are in parallel, the total resistance is less than the resistance of the individual resistors. this is because there are more paths for the current

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23
Q

in order to test or measure the resistance of a component you must have?

A
  • a variable resistor
  • ammeter
  • voltmeter
  • bulb
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24
Q

resistance decreases as light intensity …..

A

increases

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25
Q

is resistance higher in the dark or light?

A

the dark

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26
Q

real life examples of light dependant resistors?

A
  • street lamps that turn on and off automatically
  • automatic flash settings on a phone
  • automatic headlights in car
  • security systems
  • animal cameras
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27
Q

what is a thermistor?

A

a resistor whose resistance depends on temperature

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28
Q

resistance decreases as temp ……..

A

increases

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29
Q

is resistance higher in the hot or cold?

A

the cold

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30
Q

real life examples of thermistors?

A
  • automatic thermostat
  • temp warning lights
  • ovens/microwaves
  • vehicles - temp warning lights
  • digital thermometer
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31
Q

what is a diode?

A

a component that passes current in one direction but not the other

32
Q

what is a light dependant resistor?

A

a component with resistance that increases when the light intensity decreases

33
Q

what is a thermistor?

A

a component with resistance that decreases when the temp increases

34
Q

what causes the wire inside a filament bulb to heat up when electrical charge flows through it?

A

resistance

35
Q

what happens if a component is disconnected from a series circuit?

A

the circuit has been broken so stops working

36
Q

what happens if a component is disconnected from a parallel circuit?

A

the current flows down a different path so keeps working

37
Q

disadvantage of series circuits?

A

if one stops working, they all stop working

38
Q

advantage of series circuit?

A

its simple, because all the bulbs are controlled with one switch

39
Q

how can a plane become electrically charged while flying?

A

the electrons are transferred due to friction, leaving a charge on the aircraft

40
Q

what is a danger of fuelling an electrically-charged aircraft?

A

a spark

41
Q

how does connecting the safety wire reduce possible dangers when fuelling an electrically-charged aircraft?

A
  • charge flows through the wire
  • it discharged the aircraft by moving the charge to the ground
42
Q

why are electrical wires wrapped in insulating materials?

A

to help minimise the risk of electrocution

43
Q

what is a fuse?

A

a component which will break if too much current flows through it

44
Q

what happens if the current in a fuse is too high?

A

the temp is higher than the wire in the fuse can take and so it melts breaking the circuit, making the device safe

45
Q

earth wire?

A

connects to the earth so that excessive charge will conduct and dissipate into the ground

45
Q

live wire?

A

connects device to 230V mains electricity. passes through the fuse

46
Q

neutral wire?

A

completes the circuit

47
Q

why are circuit breakers more convenient than fuses?

A
  • a fuse breaks if too much current flows through it, meaning it can only be used once
  • circuit breakers detect surges in current
  • when a surge is detected, a switch is opened, immediately breaking the circuit
  • circuit breakers can be reset by flicking the switch back to its original position
  • this makes them more convenient as they can be reused
48
Q

why are wires made of copper?

A

it is a good conductor of charge, it allows current to flow

49
Q

why are wires covered in flexible plastic?

A

it is a good insulator of charge, prevents electric shock

50
Q

why is the earth wire longer than the others in a plug?

A

so the circuit can’t be used without an earth wire

51
Q

which direction do charges move in direct current?

A

all charges move in one direction around the circuit, so voltage is either positive or negative

52
Q

what provides the charge in a direct current?

A

batteries and cells

53
Q

which direction do charges move in alternating current?

A

charges constantly change direction (back and forth), so voltage goes between being positive and negative

54
Q

what provides the charge in an alternating current?

A

mains power supplies

55
Q

how does heating happen in electric circuits?

A
  • a resistor contains an ion lattice
  • when electrons collide with the ionic lattice they transfer energy to heat
  • this is the heat that dissipates into the surroundings
56
Q

advantage of heating effect in electric circuits?

A

some components want to heat, like electric heaters

57
Q

disadvantage of heating effect in electric circuits?

A
  • wasted heat energy costs money and resources
  • if some components get too hot, they can stop working or catch fire
58
Q

what is the relationship between energy, voltage and charge

A

energy = charge x voltage

59
Q

what is the relationship between power, energy and time?

A

power = energy/time

60
Q

energy transferred equation?

A

energy transferred = current x time x voltage

61
Q

relationship between power, current and voltage?

A

power = current x voltage

62
Q

what type of current is mains electricity

A

alternating current (a.c.)

63
Q

what type of current is being supplied by a cell or battery

A

direct current (d.c.)

64
Q

what happens to the current if the voltage increases

A

the current increases

65
Q

what happens to the current if you increase the resistance

A

less current will flow

66
Q

current in diodes

A

current can only flow through in one direction

67
Q

what can lamps and LEDs be used to do

A

indicate the presence of a current in a circuit

68
Q

what is electric current in solid metallic conductors

A

a flow of negatively charged electrons

69
Q

everyday materials that are electrical conductors

A

copper, brass, steel, gold, aluminium

70
Q

everyday materials that are electrical insulators

A

rubber, plastic glass, wood

71
Q

practical: investigate how insulating materials can be charged by friction

A

1) POLYTHENE AND ACETATE RODS
- rub polythene and acetate rods with a cloth duster
- when polythene rod is rubbed with duster, electrons move from duster to rod -> rod becomes negatively charged
- when acetate rod is rubbed with duster, electrons move from rod to duster -> rod becomes positively charged

72
Q

how are positive and negative electrostatic charges produced on materials

A
  • electrons are negatively charged
    -> when a material loses electrons, it loses that negative charge and becomes positively changed
    -> when a material gains electrons, it gains that negative charge and becomes negatively charged
73
Q

forces of attraction between…

A

opposite charges

74
Q

forces of repulsion between….

A

alike charges

75
Q

uses of electrostatic charges

A

1) INKJET PRINTER
- tiny droplets of ink are forced out a fine nozzle, making them charged
- droplets are deflected as they pass between two metal plates
-> voltage is applied to the plates - one is negative one is positive
- droplets are attracted to plate with different charge and repelled from plate with same charge
-size and direction of voltage across each plate changes so each droplet is deflected to hit a different place on the paper

2) PHOTOCOPIER
- image plate is positively charged
- lighter bits of what your photocopying make light fall onto plate and charge leaks away in those places
- charged bits attract negatively charged black powder
- paper is heated so powder sticks

physics (8 decks)

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