Question

Explain the meaning of the statement ‘current rating of a fuse $5A$’.

Answer 1

Hint: In this question first of all we will explain what is electric fuse and the principle on which the electric fuse works and that is the heating effect of electric current when passed through the conductor and then we will explain how it works for the safety of electric circuits.

Using Formula: -
When an electric current $I$ is flowing through a conductor of resistance $R$ across the potential difference $V$ then heat produced $H$ is as follows:
$H = VI$
$H = {I^2}R$
$H = \dfrac{{{V^2}}}{R}$

Complete step-by-step answer:
Given Data: -
An electric fuse of rating $5\,{\rm A}$.
Electric fuse
It is an electrical safety device which operates in order to provide over current protection of an electrical circuit. It consists of a metal wire or strip that melts when over current passes through it. In this way it interrupts the current by its own sacrifices that is why it is also known as a sacrificial device.
Heating effect of current
When electric current is passed through a conductor having resistance then it gets heated due to the current in it. This effect is known as the Heating effect of current.
The heat produced in the conductor is proportional to the applied voltage, current through it and resistance of it as given in the formulae.
$H = VI$
$H = {I^2}R$
$H = \dfrac{{{V^2}}}{R}$
The wire of the fuse is designed to get the desired value of current by adjusting the thickness of the wire and length of the wire that is the rating current of the electrical fuse above which if current increases in the circuit then it will melt and break the circuit.
Hence the meaning of the statement ‘current rating of a fuse $5\,{\rm A}$’ is that when an electric current more than $5\,{\rm A}$ is passed through, it will melt and the supply will break to save the appliances.

Note: To answer this question we will not miss to describe the definition of electric fuse and principle on which it works and how it works.