11. Exercises XI

1. When does an electric short circuit occur? 

 

OverloadingOpen Circuit can happen when the live wire and the neutral wire not in the direct contactcome into direct contact. (This happens when the insulation of wires is damaged or there is a defect in the appliance.) In these situations, the current in the circuit suddenly decreasesincreases. This is called short-circuiting.

 

2. What is the function of an earth wire? Why is it necessary to earth metallic appliances?

 

The earth wire, which has red colourgreen colourblack colour insulation, is generally attached to a metal plate deep in the earth near the house. This is used as a safety measure, particularly for appliances with a metallic body.

 

The metallic body is attachedis not attached to the earth wire, which provides a low-resistancehigh-resistance conducting path for the current. Thus, it assures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, and the user may not get a severe electric shockmay get a severe electric shock.