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Domestic Electric Circuit

Domestic Electric Circuit

1.     Household electric supply consists of 3 types of wire. Live wire (red insulation cover), neutral wire (black insulation cover) and earth wire (green insulation cover)
2.    The potential difference between neutral and live wire is 220V.
3.    In household circuit system, two type of circuit are used. One of 15 A for appliances with higher power ratings and the other of 5 A ratings for bulbs etc.
4.    In domestic circuit, different appliances are connected in parallel combination. This ensures that if one appliance is switched ‘on’ or ‘off’, the others are not affected.
5.    The earth wire is used as a safety measure, especially for those appliances that have a metallic body.

Working of earth wire 

The metallic body is connected to the earth wire, which provides a low resistance-conducting path for the current. It ensures that any leakage of current to the metallic body of the appliance will flow to the earth only and the user may not get a severe shock.

Short circuit

It means that the two wires live and neutral have come in contact with each other. This may happen either due to their insulation have been damaged or due to a fault in the appliance. In such a case, the resistance of the circuit decreases to a very small value. According to Ohm’s law, the current increases enormously. It may results in spark at the place of short circuit, which may even cause fire. Sometimes, the current also increase due to overloading of the circuit.


It is a situation when too many appliances are connected in the same circuit such that the overall current (sum of all the current used by all appliances) exceeds the current carrying capacity of the connecting wires. The wires cannot withstand such a high current and melt and may cause fire. 

The electric fuse

Electric fuse is used as safety device for the protection of electric circuits and appliances due to short circuiting or overloading of the circuit.. The electric fuse is a piece of wire having a very low melting point and high resistance.When a high current flows through the circuit due to short circuit or overloading, the fuse wire gets heated and melts. The circuit is broken and current stops flowing thus save the electric circuit and appliance form damage.

Capacities of fuse wire

The fuse for domestic purposes are rated as 1A, 2A, 3A, 5A, 10A and 15A.         

Characteristics of fuse wire

1.    Low melting point
2.    High resistance 

Fuse wire are made up of pure tin or made of an alloy of copper and tin.              


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