Question

An electric bulb is rated 220 V and 100 W. Power consumed by it when operated on 110 volt is

• A. 50 W
• B. 75 W
• C. 90 W
• D. 25 W

Answer 1

Answer: (D)

25 W

Answer 2

By using $P_{consumed} = \left( \frac{V_{A}}{V_{R}} \right)^{2} \times P_{R}$

⇒ $P_{Consumed} = \left( \frac{110}{220} \right)^{2} \times 100 = 25W$