Main electricity

Live: Brown: This supplies the AC current, its voltage is 230V. (alternating current)

Neutral: Blue: This completes the circuit.

Earth: Green/yellow: This is connected to a metal casing of an appliance. Appliances without metal casing do not need it.

AC current

  • The current supplied in UK plugs is Alternating current. This means it continuously keeps changing direction and magnitude 50x a second.

DC current

  • The current flows in one direction only.

Fuse

  • Contains a thin wire with a low melting point that melts if the current becomes too large, disconnecting the device.

  • Protects wires and devices from overheating/fire.

Earth wire

  • If a device with a metal casing becomes faulty, the casing can be live. A person could get a shock.

  • Earth wire is connected to the casing, a large current will surge through to the ground, this large current melts the fuse on the live wire, disconnecting the device.

Double insulation

  • The device has a non-conducting case (plastic), so this device does not need an earth wire.

Energy transferred = Power*time

P=VI

  • P = Electrical power [W] watts

  • V = Voltage [V] volts

  • I = Current [A] amps

A device requiring larger power requires a large current and will need thicker (lower resistance) wires to prevent the wires from overheating.

Electrical energy

  • E=Pt=VIt

    • E = electrical energy (transferred) [J] joules

    • P = Power [W] watts

    • t = time [s] seconds

    • V = Voltage [V] volts

    • I = Current [A] amps

Dangers

  • Damaged insulation

    • Contact with the wire due to gaps in the insulation can cause an electrical shock or pose a fire hazard by creating a short circuit

  • Overheating of cables

    • High currents passing through thin wire conductors can cause the wires to heat up very high temperature which can melt the insulation and cause a fire.

  • Damp conditions

    • Water can conduct a current so wet electrical devices can cause an electrical shock.