Domestic Uses and Safety

Is mains electricity and a.c supply or a d.c supply? What do they stand for?

• mains electricity is a.c supply

• a.c alternating current

• d.c direct current

Define alternating current and direct current

• alternating current - current that continuously changes direction in a specific frequency

• direct current - one directional current flow

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

• frequency - 50 Hz

• voltage - 230 V

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

1. Live wire

2. Neutral wire

3. Earth wire

State the insulation colour used on the Earth wire

green and yellow stripes

State the insulation colour used on the Live wire

brown

State the insulation colour used in the Neutral wire

blue

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

• under normal circumstances, no current flows through the Earth wire

• if a fault occurs in the appliance (such as a surge or casing becoming live) current will flow to the ground

What potential is the Neutral wire at?

0 volts

State the potential difference between the Live and Earth wires

230 Volts

What is the purpose of the Neutral wire?

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

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

• 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 Earth wire, preventing electrocution