Question

If a bulb is rated at 500w at 100v used in a circuit having 200v. The resistence 'r' must be kept in series with that bulb so that the bulb draws 500w

Answer 1

power of bulb in 100 v is 500 watt
current when it connected into 200 volt
p = v * i
500 = 200 * i
i= 500/200
i= 2.5 A

resistance R = v / i
R = 200 / 2.5
R = 80 ohm

therfore resistance is 80 ohm


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