Section 2: Electricity

Question 1

what are the metal parts in a plug made of and why?

Answer 1

copper or bass; good conductors of electricity

Question 2

what is the voltage of the live wire and what colour is it?

Answer 2

brown - alternates between high positive and negative voltage of about 230V

Question 3

what is the voltage carried by the neutral wire and what colour is it?

Answer 3

blue - 0V

Question 4

what colour is the earth wire and what is its role?

Answer 4

green/yellow - for safety - reduces the danger of an electric shock as it prevents the conductor from becoming live

Question 5

do appliance with double insulation need an earth wire?

Answer 5

no

Question 6

what is the flow of electricity in a plug? eg which wire does it flow in, which out?

Answer 6

in through the live wire, out through the neutral wire

Question 7

how do fuses prevent electric shocks and fires?

Answer 7

they blow (melt) following a surge in current which cuts off the live supply, isolating the whole appliance thus making it impossible for you to get an electric shock

Question 8

how do circuit breakers work to break the circuit when the voltage is too high?

Answer 8

when circuit breakers detect a surge in current they break the circuit by opening a switch

Question 9

what are some advantages of circuit breakers over fuses?

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Answer 9

1. circuit breakers and their circuit can easily be reset by flicking a switch on the device - unlike fuses, they don’t need to be replaces
2. they act faster, as soon as there is current surge; no time is wasted waiting for the fuse to melt
3. they even work for small current surges, which might not be enough to melt a fuse - even small current changes can be fatal

Question 10

what happens to resistors when there is an electric current?

Answer 10

there is an energy transfer which heats the resistor

Question 11

what is the effect of the heat created when there is an electric current on the resistor?

Answer 11

it increases the resistor’s resistance, so less current will flow or a greater voltage will be needed to produce the same current

Question 12

what is the unit for power?

Answer 12

watts

Question 13

what are the 3 most common fuse ratings used in the UK?

Answer 13

2A , 5A, 13A

Question 14

should you always choose a fuse rating that is higher or lower than the normal current?

Answer 14

higher

Question 15

what is meant by the word current? unit?

Answer 15

the rate of flow of charge round the circuit - needs voltage to flow A

Question 16

what is meant by the word voltage? unit?

Answer 16

pushes the current round V

Question 17

what is meant by resistance? unit? what is the effect of adding more components to a circuit on the resistance?

Answer 17

anything in the circuit which slows the flow of electrons down - adding more components means more resistance - ohms

Question 18

what does an ammeter do?

Answer 18

measures the current in amps flowing through the component

Question 19

what kind of circuit can ammeters be placed in? (series/parallel)

Answer 19

series

Question 20

what does a voltmeter do?

Answer 20

measures the voltage across the components

Question 21

what kind of circuit must voltmeters be placed in?

Answer 21

in parallel arounfd the component under test - not around variable resistor/battery