Question

An electric bulb is rated 220 volt 100 watt. The power consumed by it when operated on 110 volts will be

• A. $50watt$
• B. $75watt$
• C. $40watt$
• D. $25watt$

Answer 1

Answer: (D)

$25watt$

Resistance of the bulb is given by,
$R=\frac{V^2}{P}=\frac{{220}^2}{100}=484\Omega$
Power consumed by the bulb when operated on 110V,
$P=\frac{V^2}{R}=\frac{{110}^2}{484}=25W$