Question

The current in a kettle is 10 A and the kettle is protected by a 13 A fuse. The owner of the kettle replaces the 13 A fuse with a 3 A fuse. What happens when the kettle is switched on?
(A) The fuse melts and the kettle might be damaged
(B) The fuse melts and the kettle is undamaged
(C) The fuse does not melt and the kettle works correctly
(D) The fuse does not melt but the kettle fails to work

Answer 1

Hint: We are given that the kettle uses 10A of current for its normal operation. A 13A fuse is put there to protect the kettle in case it draws a high current which will damage the kettle. If this fuse is replaced by a 3A fuse, the fuse will break as it will try to draw in 10A. this breaking of the fuse will break the connection and the kettle will remain unusable until the fuse is replaced.

Complete Step by step answer
Firstly, let us understand what a fuse is and what its purpose is. A fuse is an electrical safety device that operates in an electrical circuit to protect from any harmful excess current that might flow in the circuit. The fuse has a metal strip or metal wire with a current rating. If a current above the current rating flows through it, the fuse wire melts and breaks the circuit. The circuit now becomes an open circuit and doesn’t allow the high current value to flow through other devices in the circuit and hence, saves them from any sort of damage. In the question, the current flowing through the circuit is 10 A. The 13 A fuse will allow currents up to 13 A to pass through itself and the rest of the circuit, including the kettle. When the 3 A fuse is used, it would only allow currents up to 3 A to flow through the circuit. When the switch is turned on, the fuse wire of the 3 A fuse will melt, the circuit will break, the current flowing through the circuit will stop and there will be no damage to our kettle.

Therefore, option(B) is correct.

Note: A fuse is a sacrificial device, i.e. the wire inside the fuse which makes the connection completely melts down and breaks the circuit to prevent any damage to other components of the circuit. Hence, a fuse can do this only once, it will have to be replaced or rewired for making it operational once again.