Physics (NTSE/Olympiad)  

2. Magnetic Effect of Current

Earthing , Overloading & Short Circuits

Earthing , Overloading & Short Circuits
Definition : Connecting the metallic body of a high powered electrical appliance (e.g. electric iron, refrigerator, oven, etc.) to the earth wire of domestic circuit, is called ‘earthing’.

In three pin plug, has three pins forming a triangle. The upper pin is thicker than the two lower pins. (fig.) The pins are connected inside the body of the plug to the three different coloured wires of a three–cored, wire cable [Fig.]. The colour code of the wires is green (Earth–E), Red (Live–L), Black or Brown (Neutral–N).
Benefits : Due to wear and tear with long use, the live wire inside the appliance becomes bare (uncovered) and touches the body of the applicance. This contact raises the potential of the body to the huge potential of the live wire. If we operate that appliance with bare foot, we will be getting a severe shock.
If the appliance is earthed, its body potential remains zero due to contact with the earth. Nothing is felt when such an appliance is operated.
We may conclude that we save ourselves from severe electric shocks, by earthing our electrical appliances.

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