# A 100 W – 220 V bulb is connected to 110 V source. Calculate the power consumed by the bulb.

Q: A 100 W – 220 V bulb is connected to 110 V source. Calculate the power consumed by the bulb.

Sol. Power of the bulb, P = 100 W

Operating voltage, V = 200 V

Resistance of the bulb, $R = \frac{V^2}{P}$

$R = \frac{200^2}{100}$

R = 484 Ω

Actual operating voltage, V’= 110 V

Therefore, Power consumed by the bulb,

$\large P’ = \frac{V’^2}{R} = \frac{110^2}{484}$

= 25 W