An electric bulb rated as 200 W at 100 V is used in a circuit having 200 V supply. The resistance R that must be put in series with the bulb so that the bulb delivers the same power is ______ Ω .

Step-by-step solution

Power, P = V 2 R B R B = V 2 P = 100 × 100 200 R B = 50   Ω To produce same power, same voltage (i.e., 100   V ) should be across the bulb. Hence, R = R B R = 50   Ω