Mains Electricity

Question 1

which two wires are in a two core cable

Answer 1

live wire and neutral wire, no need for earth wire as it is either double insulated or entirely plastic

Question 2

why do devices with plastic casing not need an earth wire

Answer 2

plastic is an insulator NOT a conductor

Question 3

state the frequency and voltage of UK mains supply

Answer 3

50Hz frequency and 230v PD

Question 4

what is a.c

Answer 4

alternating current- current which changes direction constantly

Question 5

colours of each wire in a plug

Answer 5

blue-neutral
brown-live
green and yellow-earth

Question 6

what type of fuse is needed in a plug for an oven operating at 14A- 10A, 14A or 18A

Answer 6

18A- the fuse rating must be higher than the operating current

Question 7

describe what happens when a fault occurs in an electrical device

Answer 7

current flows from live to earth which blows or melts the fuse. The circuit is broken and the metal casing is no longer live

Question 8

2 advantages of an RCCB over a Fuse

Answer 8

• it can be reset
• It is more sensitive than a fuse and therefore safer
• it is faster to act

Question 9

what does RCCB

Answer 9

residual current circuit breaker

Question 10

describe how an RCCB works

Answer 10

it detects a difference in current between a live and neutral wire

Question 11

how is the wire in a 1A fuse different to one in a 5A fuse

Answer 11

the wire is thicker in a 5A fuse

Question 12

why would a device be fitted with a 2 core cable

Answer 12

if it was double insulated or had plastic casing

Question 13

why do faults occur in electrical devices

Answer 13

the live wire comes loose and touches the metal case which causes the casing to become live