An electric appliance is protected by a fuse that must melt if the current exceeds
PHYSICS · Multi-part · CBSE · Physics · Electricity: Magnetic and Heating Effects · Electricity: Magnetic and Heating Effects
Problem
An electric appliance is protected by a fuse that must melt if the current exceeds 6A. The fuse element is made of an alloy whose resistivity is 1.4×10−7Ωm. The fuse is to be a straight wire 20mm long.
The fuse material melts when 1J of heat is produced per millimetre of its length in 0.20s. Ignore heat losses to the surroundings.
(a) Derive an expression for the heat produced in the fuse element in a time t when a current I flows through it.
(b) Using the given data, calculate the maximum resistance the fuse element may have.
(c) Hence determine the required diameter of the fuse wire. Give your answer to the nearest 0.01mm.