what is the use of neutral wire ????? pls explain

also tell what is its potential????

Dear Shivam,

The neutral wire just completes the circuit back to the power souce. If you don't have a complete path back to the source there is no current flow. It is NOT excess current. Consider a light bulb, you certainly wouldn't expect it to light up if you only hooked it to one wire from the power souce.
In home wiring, the neutral is typically grounded at the power source, but current doesn't flow to ground unless there is something faulty in path somewhere. Grounding the neutral protects us be insuring that there isn't a voltage on the neutral wire if something goes wrong.

  It's potential is equal to Ground Potential, i.e. 0.

       God Luck!!!!!

  Plz. Plz. approve it!!!!!!!1