Question

An electric bulb is rated (60W, 220 V). If it is operated at 110 V, then find the power consumed by it.

Answer 1

(60W,220V) means the bulb will consume 60 W power when it is connected to a supply of 220 Volts.
Rated Power (P)=60W
Rated Voltage (V)=220V
we known
Power(P)=v^2/R
So
Resistance of the bulb
R=(V^2)/P
=(220×220)/60
=48400/60
=806.67ohms

• Resistance of the bulb remains same for any applied voltage

​​​​​​​​​​​
power ,P=V^2/R
​​​​​​​ Applied voltage = 110v
So
Power,P= (110×110)/806.67
=12100/806.67
=14.999W