8) Electricity in the home

Alternating Current (AC) vs. Direct Current (DC)

• Alternating Current (AC): The current changes direction, created by alternating voltages. Mains supply (UK) is AC at 230V and a frequency of 50 Hz.

• Direct Current (DC): Flows in one direction only, produced by direct voltage. Batteries and cells supply DC.

Wires in Electrical Cables

Electrical appliances typically connect to mains supply with three-core cables—copper wires coated with colored plastic. Each color signifies a wire’s purpose:

1. Live Wire (Brown): Provides the alternating potential difference (230V) from mains supply.

2. Neutral Wire (Blue): Completes the circuit. Around 0V.

3. Earth Wire (Green and Yellow): For safety; it stops the appliance casing from becoming live. Only carries current in a fault, also at 0V.

Electric Shock Risks

• Live Wire Danger: If you touch the live wire, a potential difference (pd) is created across your body (which is at 0V), leading to current flow and electric shock.

• Switch Safety: Even if a switch is off, the live wire can still have a pd, so touching it could link you to the earth and cause current flow.

• Earth Connection Hazards: If a low resistance path between live and earth is created, a large current could flow, posing a major shock risk.