Question 1: Define the primary function of the Live wire in a mains electrical system.

Answer: The Live wire carries the alternating voltage from the power supply to the appliance.

Question 2: Explain why the Neutral wire is usually at or near earth potential.

Answer: Because it is connected directly to the earth at the substation, maintaining a zero potential difference.

Question 3: What is the purpose of the Earth wire in household wiring?

Answer: To provide a safe path for current to flow to the ground in case of a fault, preventing electric shocks.

Question 1: A household circuit shows a potential difference of 230 V between Live and Neutral wires, with a current of 3 A flowing through an appliance. Calculate the power consumed by the appliance. (Use P = V × I)

Answer: 690 Watts

Question 2: In a certain wiring setup, a fault causes the Earth wire to carry a current of 5 A. Explain the safety implications of this situation.

Answer: This indicates a fault where live current is leaking to the Earth wire, which can be dangerous and may cause electric shocks or fires. Immediate inspection and repair are required.

Question 3: If an appliance's Earth wire is disconnected, what potential hazards could occur?

Answer: The appliance could become live if its casing is conductive, increasing the risk of electric shock.

Question 1: List three safety precautions that should be taken when working with mains wiring in a household.

Answer: Turn off the mains supply, wear insulated gloves and tools, and check that the circuit is de-energised before starting work.

Question 2: Describe a simple experiment to verify that the Neutral wire is at or near earth potential.

Answer: Use a voltmeter to measure the potential difference between the Neutral wire and an earth point. A reading close to 0 V confirms it is at earth potential.

Question 1: Explain how the Earth wire enhances safety in the design of household electrical appliances.

Answer: The Earth wire provides a low-resistance path for fault current, ensuring that in case of a live wire contact with metallic parts, the current flows safely to ground, causing the fuse to blow and preventing electric shocks.

Question 2: Identify one industry standard or regulation related to the wiring of Live, Neutral, and Earth wires in the UK.

Answer: The wiring must comply with BS 7671 (IET Wiring Regulations), which specify correct connections and safety measures.