Question

The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 W and 200 V lamp when not in use?

• A. 40 W
• B. 20 W
• C. 400 W
• D. 200 W

Answer 1

Answer: (A)

40 W

Answer 2

R_{Hot bulb} = $\frac{V^{2}}{P}$ = $\frac{200 \times 200}{100}$ = 400 W