Mains Electricity Flashcards
which two wires are in a two core cable
live wire and neutral wire, no need for earth wire as it is either double insulated or entirely plastic
why do devices with plastic casing not need an earth wire
plastic is an insulator NOT a conductor
state the frequency and voltage of UK mains supply
50Hz frequency and 230v PD
what is a.c
alternating current- current which changes direction constantly
colours of each wire in a plug
blue-neutral
brown-live
green and yellow-earth
what type of fuse is needed in a plug for an oven operating at 14A- 10A, 14A or 18A
18A- the fuse rating must be higher than the operating current
describe what happens when a fault occurs in an electrical device
current flows from live to earth which blows or melts the fuse. The circuit is broken and the metal casing is no longer live
2 advantages of an RCCB over a Fuse
- it can be reset
- It is more sensitive than a fuse and therefore safer
- it is faster to act
what does RCCB
residual current circuit breaker
describe how an RCCB works
it detects a difference in current between a live and neutral wire
how is the wire in a 1A fuse different to one in a 5A fuse
the wire is thicker in a 5A fuse
why would a device be fitted with a 2 core cable
if it was double insulated or had plastic casing
why do faults occur in electrical devices
the live wire comes loose and touches the metal case which causes the casing to become live
