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electricity Flashcards

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1
Q

what is a circuit

A

a closed loop that contains a power source and something for electrons to flow through

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2
Q

what is current and what is it measured in

A

a measure of the flow of electrons around the circuit, it is measured in amperes

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3
Q

what is potential difference/voltage and what is it measured in

A

force driving the flow of electrons and is provided by a cell or battery, measured in voltage

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4
Q

what is resistance and what is it measured in

A

everything that resists or opposes the flow of electrons, it is measured in ohms

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5
Q

which way does a circuit current flow

A

from the negative terminal to the positive terminal, in our exams it is from positive to negative (conventional current)

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6
Q

what is the equation for potential difference

A

V = IR

potential difference = current x resistance

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7
Q

what happens to resistance when you increase temperature

A

when temperature increases so does resistance

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8
Q

what is charge

A

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

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9
Q

what is charge measured in

A

coulombs (C)

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10
Q

what is the equation for charge

A 
Q = I x t
charge = current x time
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11
Q

what does a fuse do

A

break if too much current flows through the circuit (used for safety)

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12
Q

what does a diode do

A

only allows current to flow in one direction

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13
Q

what does an ammeter do and how is it connected to the circuit

A

measures current and is connected in series

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14
Q

what does a voltmeter do and how is it connected

A

measures the voltage and is connected in parallel

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15
Q

what does a resistor do

A

it restricts the flow of electric current

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16
Q

what is an light-dependent resistor

A

a resistor which resistance is dependent of the intensity of light

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17
Q

what is a thermistor

A

a resistor which is dependent on temperature

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18
Q

what is a series circuit

A

a circuit which only has a single loop

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19
Q

what is a parallel circuit

A

a circuit that has more than one loop

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20
Q

what happens if a component is damaged or removed in a series circuit

A

the whole circuit will stop working

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21
Q

what is the potential difference like across a series circuit

A

it is shared across all of the components

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22
Q

what is current like across the circuit

A

current is the same everywhere across the circuit

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23
Q

what is resistance like across a series circuit

A

different components might have different resistances and the total resistance is the sum of all of the different resistances

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24
Q

why are parallel circuits usually more useful than series circuits

A

if one component breaks, the overall circuit is still intact

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25
Q

what is voltage like across a parallel circuit

A

all components get the full source of potential difference

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26
Q

what is current like across a parallel circuit

A

current is shared across the the parallel circuit, loops might have different currents

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27
Q

what is resistance like across a parallel circuit

A

more components in parallel = lower total resistance

28
Q

what is the national gird

A

the national grid is the network of cables and transformers that transport electricity from the power stations to our homes, factories, offices, shops and other places that require it

29
Q

how do power stations work

A

by generating a lot of heat and then converting that into electrical energy

30
Q

how do power stations cope with surges in demand for energy

A

the have spare capacity and often run below their maximum power output

31
Q

why is the current kept low across the national grid

A

high current means lots of energy will be lost as heat to the surrounding so the current has to be kept low while the voltage is very high

32
Q

what do step-up transformers

A

the increase the voltage to 400,000 V

33
Q

what do step-down transformers do

A

decrease the voltage to 230 V so it is safe for our homes and buildings

34
Q

what is the formula for power

A 
power = voltage x current 
power = current^2 x resistance
35
Q

what are the two types of current

A
  • alternating current (A.C)

- direct current (D.C)

35
Q

what are the two types of current

A
  • alternating current (A.C)

- direct current (D.C)

36
Q

how does the charge flow in an alternating current

A

it is always changing direction

37
Q

give an example of A.C

A

mains supply is A.C

38
Q

what is the voltage of mains supple

A

230 V

39
Q

what is the frequency of mains supply

A

50 Hz

40
Q

what is direct current produced by and how does it flow

A

it is produced by a direct potential difference and is either negative or positive the entire time, therefore the charge is always flowing in the same direction

40
Q

what is direct current produced by and how does it flow

A

it is produced by a direct potential difference and is either negative or positive the entire time, therefore the charge is always flowing in the same direction

41
Q

give an example of D.C

A

cells/batteries

42
Q

what is an oscilloscopes

A

devices from which we can get potential difference vs time graphs

43
Q

what is a 3-core cable

A

a cable with 3 wires inside of it

44
Q

what are the different wires in a three-core cable

A
  • live
  • neutral
  • earth
45
Q

what are the wires in a 3-core cable made from

A

copper as it in a good conductor and it is coated in a layer os insulating plastic

46
Q

what colour is the live wire and what does it do

A
  • brown

- provides the alternating potential difference from the mains

47
Q

what colour is the live wire and what does it do

A
  • brown
  • provides the alternating potential difference from the mains
  • 230 V
48
Q

what colour is the neutral wire and what does it do

A
  • blue
  • completes the circuit by carrying away current
  • effectively electricity flows out of the neutral wire
  • 0 V
49
Q

what colour is the earth wire and what does it do

A
  • green and yellow
  • 0 V
  • doesn’t normally carry a current
  • stops the appliance casing from becoming live
50
Q

what colour is the earth wire and what does it do

A
  • green and yellow
  • 0 V
  • doesn’t normally carry a current
  • stops the appliance casing from becoming live
  • provides an alternative pathways for the electricity to pass through
51
Q

what happens if humans touch the live wire

A

it will create a large current to flow in the form of an electric shock

52
Q

what is a surge

A

a sudden increase in current

53
Q

what is a fuse (not in a circuit)

A

a very thin piece of wire

- which will melt and break the circuit if there is a surge

54
Q

what is the advantages and disadvantages of fuses

A
  • simple and cheap

- but they are permanently broken after a single surge

55
Q

what is a circuit breaker

A

break the circuit when there is a surge

  • they aren’t permanently damaged and only trip to turn of the circuit
  • can be reset
56
Q

what is earthing

A

if the live wire is touching the casing the earth wire will provide an alternate pathway for the current so that we don’t get an electric shock

57
Q

what is double insulation

A

covering the entire appliance in a plastic casing so that no metal is exposed

58
Q

what is static electricity

A

build up of charge on insulating materials

59
Q

how does friction transfer electrons

A

rubbing two objects together means electrons will rub off of one object to another and cannot flow back as they are insulating materials

60
Q

what happens when an object gains too many electrons

A

a potential difference is developed with the charged material and any earthed object

  • if the pd is great enough electrons can jump across the gap
  • this creates a spark
61
Q

how are electric fields represented in physics

A

in field lines that go from positive to negative

62
Q

describe the strength of an electric field

A

it is the strongest close to the particle and gets weaker the further away you get

63
Q

what is ionisation

A

when a strong electric field causes air particles to lose their electrons and conduct electrify
- this is how sparks can travel

physics (5 decks)

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