Question

An electric bulb is marked $100$W, $230$V. If the supply voltage drops to $115$V, what will be the total heat and light energy, total liberated by the bulb in $20$ minutes?

Answer 1

The bulb is rated $100W,220V.$

The maximum current drawn by the bulbis given by,

$I=\frac{P}{V}$

$=\frac{100}{220}=\frac{5}{11}A$

when the voltage is $115V$ then, the power consumed canbe given as

$P=VI$

$=115\times \frac{5}{11}=52.28J/s$

But it is lighted for $20min$ So, the total energy consumed is given by

$E=P\times T=52.28\times 20\times 60=62736J$

$\therefore 62736J$will be liberated by thhe bulb in $20min$ in form of heat and light energy.