Question

An electric bulb rated 200 V and 100 W is connected to a 160 V power supply. The power consumption would be

• A. 64 W
• B. 80 W
• C. 100 W
• D. 125 W

Answer 1

The correct option is A 64 W

We know that the power is directly proportional to the ratio of the square of the voltage to the resistance.

It is given as $P=VI$

That is, $P=\frac{V^2}{R}asI=\frac{V}{R}$.
As the resistance remains the same through out, the above equation can be written as $P\propto V^2$
So, with the values given in the question, $\frac{P_2}{P_1}={\left(\frac{V_2}{V_1}\right)}^2$.
That is, $P_2=P_1{\left(\frac{V_2}{V_1}\right)}^2=100\times {\left(\frac{160}{200}\right)}^2=64W$.

Hence the power consumption would be 64 W.