Question

Figure shows a 3-pin plug with the cover removed. The electric cable connected to the plug contains 3 wires with colour-coded insulation, namely, brown, blue and green.

1. Identify each of the colour-coded wires by stating to which of the terminals A, B or C in the diagram they should be connected.
2. Identify the terminal through which no current passes in normal circumstances.
3. What is the purpose of the earthed wire connected to an electric appliance like an electric heater? Describe how it works.

Answer 1

(a) Identification of colour-coded wires,

• A: Green (Earth wire)
• B: Blue (Neutral wire)
• C: Brown (Live wire)

(b) Terminal through which no current passes, Terminal A (Earth terminal) carries no current under normal circumstances.

(c) Purpose of the earth wire, the earth wire protects a person from electric shock by connecting the metal body of the appliance to the ground.

If the live wire accidentally touches the metal body, a large fault current flows through the earth wire, causing the fuse to melt and break the circuit, preventing electric shock.