Question

An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be ______.

पर्याय

• 100 W

• 75 W

• 50 W

• 25 W

Answer 1

An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be 25 W.

Explanation:

Resistance of the bulb

∴ P = ${\displaystyle \frac{{\text{V}}^2}{\text{R}}}$

R = ${\displaystyle \frac{{\text{V}}^2}{\text{P}}}$

= ${\displaystyle \frac{220{\text{V}}^2}{100}}$

= 484 Ω

Then, Power consumed at 110 V

P' = ${\displaystyle \frac{{\left(\text{V'}\right)}^2}{\text{R}}}$

= ${\displaystyle \frac{110{\text{V}}^2}{484}}$

= 25 W