Domestic Electric Circuits

In our homes, the electric power supplied is of potential difference V = 220V and frequency 50Hz. It consists of three wires: –

  • Wire with red insulation cover– Live wire (+ve) Live wire is at high potential of 220V
  • Wire with black insulation cover – Neutral wire (-ve) Neutral wire is at zero Potential Therefore, the potential difference between the two is 220V.
  • Wire with Green insulation cover – Earth wire It is connected to a copper plate deep in the earth near house.
  • The metallic body of the appliances is connected with the earth wire as a safety measure.
  • Earth wire provide a low resistance to the current hence any leakage of current to the metallic body of the appliances, keep its potential equal to that of earth. That means zero potential and the user is saved from severe electric shock.

Point to be noted in Domestic Circuit

  • Each appliance has a separate switch of ON/OFF
  • In order to provide equal potential difference to each appliance, they should be connected parallel to each other. So that they can be operated at any time.

Short Circuiting

  • Due to fault in the appliances or damage in the insulation of two wires, the circuit will offer zero or negligible resistance to the flow of current. Due to low resistance, large amount of current will flow.
  • According to Joule’s law of heating effect, heat is produced in live wire and produces spark, damaging the device and wiring.


Overloading can be caused by

  • Connecting too many appliances to a single socket or
  • Accidental rise in supply voltage if the total current drawn by the appliances at a particular time exceeds the bearing capacity of that wire, it will get heated up. This is known as overloading. Fuse a safety device can prevent the circuit from overloading and short circuiting.



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