2.3 Domestic uses and safety
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Is mains electricity an AC supply or a DC supply? What do each of these stand for?
Mains electricity is an AC supply. AC stands for alternating current and DC stands for direct current.
Define alternating current and direct current
Alternating current is a current that is continuously changing direction at a specific frequency. Direct current is a current with one directional 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 these wires.
● Live wire ● Neutral wire ● Earth wire
State the insulation colour used on the earth wire
Green and yellow stripes
State the insulation color used on the live wire
Brown
State the insulation color used on the Neutral wire
Blue
Explain when the earth wire does and doesn’t carry a current
Under normal circumstances, no current flows to the earth wire. If a fault occurs in the appliance (such as a surge or the casing becoming live) current will flow to the ground.
What potential difference does the neutral wire have?
0 V
State the potential difference of the earth and live wires
230 V
What is the purpose of the neutral wire?
To complete the circuit by connecting the appliance back to the main supply
For metal appliances, where is the earth wire connected to? Why?
The earth wire is connected to the metal casing of the appliance. If the live wire becomes loose and touches the casing, the current will flow through the earth wire preventing electrocution.