Question

A (100 W, 200V) bulb is connected to a to V power supply. The power consumption would be:

• A. 80 W
• B. 125 W
• C. 64 W
• D. 100 W

Answer 1

Answer: (C)

64 W

Answer 2

From the relation $P=\frac{{{V}^{2}}}{R}$ $P=100=\frac{{{(200)}^{2}}}{R}$ so, $R=\frac{{{(200)}^{2}}}{100}$ ?(i) If it is connected to 169 V then ${{P}_{1}}=\frac{{{(160)}^{2}}}{R}=\frac{{{(160)}^{2}}}{{{(200)}^{2}}}\times 100$ [from (i)] $=\frac{256}{4}=64\,watt$