Question

The largest number of 100 W electric light bulbs which can be operated from a 240 V supply fitted with a 13 A fuse is

Answer 1

Given:

$V=240\:\rm V$

$I_{\rm max}=13\:\rm A$

$P=100\:\rm W$

The maximum power in circuit

$$P_{\rm max}=I_{\rm max}V=13*240=3120\:\rm W$$

Hence, the largest number of 100 W electric light bulbs which can be operated in circuit

$$N=\frac{P_{\rm max}}{P}=\frac{3120}{100}=31$$