Topic 2- Domestic uses and safety

Question 1

Is mains electricity an a.c supply or a d.c supply? What do each of these stand for?

Answer 1

Mains electricity is an a.c supply
a.c: Alternating current
d.c: Direct current

Question 2

Define a.c and d.c

Answer 2

a.c= current that continuously changes direction at a specific frequency
d.c= one directional current flow

Question 3

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

Answer 3

Frequency: 50 Hz
Voltage: 230 V

Question 4

How many wires are usually in cables connecting electrical appliances to the mains? Name these wires.

Answer 4

3.
Live wire
Neutral wire
Earth wire

Question 5

State the insulation colour used on the earth wire

Answer 5

Green and yellow stripes

Question 6

State the insulation colour used on the live wire

Answer 6

brown

Question 7

Stater the insulation colour used on the neutral wire

Answer 7

blue

Question 8

Explain when the Earth wire does and doesn’t carry a current

Answer 8

Under normal circumstances, no current flows through the earth wire. If a fault occurs in the appliance, current will flow to the ground

Question 9

What potential is the neutral wire at?

Answer 9

0V

Question 10

State the p.d between live and earth wires

Answer 10

230 V

Question 11

What is the purpose of the neutral wire?

Answer 11

To complete the circuit by connecting the appliance back to the mains supply.

Question 12

For metal appliances, where is the Earth wire connected to and why?

Answer 12

Earth wire is connected to the metal casing of the appliance
If live wire becomes loose and touches the casing, the current will flow through the Earth wire, preventing electrocution