Question

Which safety device is used in case of overloading and short circuit?

Answer 1

Hint: In both the cases – Short circuiting and Overloading; electrical appliances are susceptible to damage due to the sharp rise in the current in the circuit. We generally use a fuse in a circuit. Purpose of the fuse is to protect home appliances from overheating and overloading.

Complete step by step solution:
1. A short circuit is a circuit where the current travels across an unintended path with low or very low electrical impedance or resistance. This travel through low resistance increases the current through the circuit as we know by Ohm’s Law that,
 \[V = IR\] where is the voltage, \[I\] is the current and \[R\] is the resistance,
Hence if the resistance drops close to zero and \[V\] is constant since it is dependent on the source of electricity, therefore \[I\] rises.
2. Overloading of the circuit is the situation when too much current passes through the circuit; this can be due to various reasons like adding a lot of resistances in parallel in the circuit.
Both of these situations lead to high current and we know that, the heat generated in an electrical circuit is given by
 \[H = {I^2}RT\] where \[I\] is the current, \[R\] is the resistance and \[T\] is the time.
Now, though the resistance in the circuit is low, since the Heat depends on the square of current, therefore in case of high current in a circuit there is a fire hazard. Hence, we can avoid this by putting a fuse in the circuit that is made of a wire with low melting point and whenever the current reaches a threshold value the circuit will get disconnected due to the melting of the fuse. Therefore, use of fuse is the most important safety method protecting home appliances from overloading or short circuiting.

Note: The fuse is safety equipment having a thin wire of short length made of \[25\% \]tin and \[75\% \] lead alloy having a low melting point. The thickness of the wire can be chosen to allow passage of a particular amount of current giving rise to a permissible amount of heat. Whenever current through the fuse exceeds the set limit, the fuse wire melts and breaks the circuit. This saves the main circuit components from damage.