Question

Choose a statement which is not correct in the case of an electric fuse.
A) Fuses are inserted in electrical circuits of all buildings
B) There is a maximum limit on the current which can safely flow through the electric circuit.
C) There is a minimum limit on the current which can safely flow in the electric circuit.
D) If a proper fuse is inserted in the circuit, it will blow off if the current exceeds the safe limit.

Answer 1

Hint: Consider the working mechanism of the fuse in the circuit. We have to keep in mind this working mechanism and try to analyze each option mentioned in the question. We have to try to match each option with the working mechanism of the fuse and find the one which doesn’t match with its working to get the answer. We have to find the principle on which fuse works for a better understanding of the topic.

Complete answer:
The electrical devices that we use in our home, work on a certain range of current. But due to short circuits or overloading, it is seen that there is a sudden increase in the current.
The increase in the current in some cases is so massive that it blows up the electrical devices and sometimes catches fire, thus damaging the property.
To prevent such mishaps, a fuse is installed in the main circuit of all the buildings so that if there is a sudden increase in the current, the fuse blows up and the circuit is broken. The heating effect of the current is the working principle of a fuse.
Only a certain amount of current is allowed to flow through the circuits, i.e. the maximum tolerance of the fuse up to which it can work smoothly. If the current overshoots the maximum limit mentioned on the fuse, the fuse wire will melt due to overheating and thus breaking the circuit.
Therefore, option (C) is incorrect as there is no minimum limit of current that has to flow through the fuse.

Note:
Nowadays, a miniature circuit breaker also known as MCB is used in the circuit instead of a fuse. MCB is an electrical switch that is operated automatically and is used to protect electrical devices from the damage caused by an excess current. MCB is more reliable than fuses as they automatically detect any abnormalities in the circuit and switch off automatically. But, if a fuse blows up, then they have to be replaced or rewired for the restoration of the electrical supply whereas in the case of MCB quick restoration is possible by flipping a switch.