Question

The voltage across an electric bulb is decreased by 2%. Assuming that the resistance of the filament remains same, the power consumed will

• A. Decrease by 2%
• B. increase by 2%
• C. decrease by 4%
• D. increase by 4%

Answer 1

The correct option is C

decrease by 4%

$P=\frac{V^2}{R}\therefore \frac{\Delta P}{P}=\frac{2\Delta V}{V}+\frac{2\Delta R}{R}$

$\frac{\Delta P}{P}=2\times 2+0=4$