Question

An iron rod consumes 400W of power, operating at 110V. What will be power consumption if it operates at 220V ?

• A. 400W
• B. 220W
• C. 1000W
• D. 1600W

Answer 1

The correct option is D 1600W

We know that
Electric Power $P=\frac{V^2}{R}$
$400=\frac{{110}^2}{R}...........\left(1\right)$
As resistance of iron will remain same,
$P=\frac{{220}^2}{R}.....\left(2\right)$
Dividing equation (2) by (1)
$\frac{P}{400}=\frac{{220}^2}{{110}^2}P=400\times 4P=1600W$