P2 : Mains electricity

Question 1

Direct Current (d.c.)

Answer 1

Direct current only flows in one direction

Question 2

Alternating current (a.c.)

Answer 2

Altenrating current constantly changes direction

Question 3

What current is UK mains electricity

Answer 3

Alternating current supply

Question 4

What is the voltage and frequency of UK mains electricity

Answer 4

230V and 50Hz

Question 5

What are the three pins in a aplug

Answer 5

Live pin, neutral pin, earth pin
The pins are made of brass, the plug contains a fuse between the live pin and the live wire

Question 6

Live wire (brown wire)

Answer 6

Carries a.c. from the supply and is dangerous

Question 7

Neutral wire (blue)

Answer 7

Completes the circuit and is usually set at 0V. It is still dangerous as a.c. flows through it

Question 8

Earth wire (green and yellow)

Answer 8

Safety wire and is set at 0V. Doesn’t normally carry current, but there is a fault, the a.c. flows from live wire to Earth

Question 9

Safety measures in plugs

Answer 9

If a fault in an appliance causes too much current flow, the fuse melts and breaks the circuit.
Circuit breakers also break the circuit when the current is too high, but are resettable by a a switch