Chapter 18, Problem 12Q

To determine

To explain:

When a low fuse of low ampere in a circuit blows out again and again, why it becomes dangerous to change it with a fuse of higher ampere

Answer to Problem 12Q

Solution:

If a fuse is blowing out, it means the current is crossing its safe limit. So, when we replace the lower ampere fuse with a higher one, actually the other appliances may be damaged.

Explanation of Solution

Formula used:

    • The Ohm’s law tells that the ratio of voltage drop (V)and the current (I)passing through a resistance (R)is ideally constant which is equal to the value of that resistance itself, i.e.,

             $R=\frac{V}{I}$

     The power consumption by a resistor is given as,

             $P=I^{2}R=V\times I=\frac{V^2}{R}$

A fuse is used to safe-guard the electric appliances connected in the circuit. Its resistance is so decided that when the current in the circuit increases to a certain limit, the fuse should blow out and start working as an open circuit. Thus, the current in the circuit stops and the important electrical appliances, connected in the circuit are safe-guarded from being damaged due to high power-loss and heating.

A 15-A fuse means that it can allow a maximum of 15-A current through it. If in a circuit it is repeatedly blowing out, it means due to some reason, the current is increasing above 15-A limit. Now if we replace it with a 25-A fuse, then it means we are allowing 25-A current to flow in the circuit.

Therefore, now the fuse may not blow out even if the current exceeds above 15-A current but it would be dangerous for the important electrical appliances, connected in the circuit because now these may be damaged due to high power-loss and heating.