Question

An electric bulb is rated at 220 volt and hundred watt it is operated on 110 volt then the power consumed will be

Answer 1

P = (v)2/r
100 = (220)2/r
100 = 48400/r
r = 48400/100
r = 484
r means resistance is taken constant
Then,
P = (110)2/484
P = 12100/484
P = 100/4
P = 25W

Answer 2

• Power = 100 W , Voltage = 220 V

P = v²/R

100 = 220²/R

R = 22²

R = 484

• Resistance = 484 ohms , Voltage = 110 V

P = v²/R

P = 110²/484

P = 25 Watt