P2.4 Using Mains Electricity Safely and the Power of Electrical Appliances

Question 1

Define alternating current.

Answer 1

Current in constantly changing direction.

Question 2

What is the frequency and voltage of mains electricity in the UK?

Answer 2

50 hertz.

About 230 V.

Question 3

Most electrical appliances are connected to the mains using a?

Answer 3

Three-pin plug.

Question 4

Describe the structure of electrical cable.

Answer 4

Earth= Yellow and Green.
Live= Brown.
Neutral = Blue.

Question 5

Which wire is attached to the fuse in a 3-pin plug?

Answer 5

Live - Brown.

Question 6

What happens if an electrical fault causes too great a current?

Answer 6

The circuit is disconnected by a fuse or a circuit breaker in the live wire.

Question 7

What happens when the current in a fuse wire exceeds the rating of the fuse?

Answer 7

Melt, breaking the circuit.

Question 8

Some circuits are protected by residential current circuit breakers, what are they?

Answer 8

Operate by detecting a difference in the current between the live and neutral wires this device operates much faster than a fuse

Question 9

Some appliances are double insulated what does that mean?

Answer 9

They have no earth wire connection.

Question 10

Describe how the earth wire and fuse together protect the wiring of the circuit?

Answer 10

When the live wire comes in contact with the metal case a large current flows. This current melts the fuse and breaks the circuit.