mains electricity

Question 1

Uk mains voltage

Answer 1

230V

Question 2

neutral wire voltage

Answer 2

0V

Question 3

live wire voltage

Answer 3

230V alternating current

Question 4

‘Earthing’

Answer 4

the case is attached to an earth wire.

Question 5

when is an earth wire not needed

Answer 5

when an appliance is double insulated

Question 6

how does a fuse and earth wire prevent fires and shocks

Answer 6

-a fault develops, and the live wire touches the case
-the case is earthed, a big current flows though the live wire the case and the earth wire
-this surge in current melts the fuse, which cuts off the live supply
-this isolates the whole appliance, making it impossible to get an electric shock from the case

Question 7

advantages of circuit breakers

Answer 7

-circuit breakers can easily be reset
-they don’t have to be replaced once they are used

Question 8

how do circuit breakers work

Answer 8

they are an electrical safety device used in some circuits
-they protect the circuit from damage if too much current flows
-they can be easily reset by flicking a witch on the device

Question 9

why would a fuse be fitted in a circuit

Answer 9

-as a safety device it reduces danger and hazards
-in case of fault/short
-excessive current of more than xA
-it prevents wires or appliances from overheating/fire

Question 10

what does a fuse do

Answer 10

it protects the circuit by:
-current increases over max value of fuse
-fuse wire melts
-cuts of current
-prevents wires in circuit from overheating

Question 11

which wire would a fuse be connected to

Answer 11

live wire