Question

Explain in brief the function of an electric fuse in a domestic circuit. An electric heater of current rating 3 kW; 220 V is to be operated in an electric circuit of rating 5 A. What is likely to happen when the heater is switched ‘ON’? Justify your answer with necessary calculation.

Answer 1

Function of an Electric Fuse
An electric fuse is a safety device used in domestic circuits to prevent overloading and short circuits. It consists of a thin wire with a low melting point. When excessive current flows through the circuit, the fuse wire melts and breaks the circuit, protecting appliances and preventing fire hazards.
Calculation
 Power of the heater ($P$) = 3 kW = 3000 W
   Voltage of the circuit ($V$) = 220 V
   Current drawn by the heater ($I$) is calculated using the formula:
$$I = \frac{P}{V}$$
Substituting the values:
$$I = \frac{3000}{220} \approx 13.64 \, A$$
    The circuit has a rating of 5 A, while the heater requires approximately 13.64 A. This current is much higher than the circuit's rating.
Likely Outcome
When the heater is switched on, the current flowing through the circuit will exceed its rated capacity (5 A). This will cause the fuse to melt and break the circuit, preventing damage to the wiring and appliances.
Justification
The fuse protects the circuit by melting when the current exceeds the safe limit. In this case, the heater requires a much higher current (13.64 A) than the circuit can handle, which will blow the fuse.