Physics – 4.4 Electrical safety | e-Consult
4.4 Electrical safety (1 questions)
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The outer casing of an electrical appliance must be either non-conducting or earthed to prevent electric shock. Here's why:
- Electric Shock Hazard: Electrical appliances often contain live (live and neutral) components. If the outer casing were live, anyone touching the appliance could receive a potentially fatal electric shock.
- Non-Conducting Casing (Double Insulation): Double insulation provides an extra layer of protection. It consists of two layers of insulation around the live parts. This prevents a person from coming into contact with the live parts, even if the inner insulation fails.
- Earthing (Grounding): Earthing involves connecting the metallic casing of the appliance to the earth wire in the electrical system.
- If a fault occurs and a live wire comes into contact with the casing, the earth wire provides a low-resistance path back to the source.
- This causes a large current to flow through the earth wire, tripping the circuit breaker or blowing the fuse, which cuts off the power supply.
- This prevents the casing from becoming live and protects the user from electric shock.
Therefore, either a non-conducting casing or earthing provides a safety mechanism to prevent electric shock in the event of a fault within the appliance.