An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be _____. (a) 100 W (b) 75 W (c) 50 W (d) 25 W

Answer: 25 W

Explanation:

The energy consumed by the appliance is given by the expression

P = VI = V²/R

The resistance of the light bulb can be calculated as follows:

R = V²/P

Substituting the values, we get

R = (220)²/100 = 484 Ω

Even if the supply voltage is reduced, the resistance remains the same. Hence, the power consumed can be calculated as follows:

P = V²/R

Substituting the value, we get

P = (110⁾² V/484 Ω = 25 W

Therefore, the power consumed when the electric bulb operates at 110 V is 25 W.