1.

An electric  bulb marked as 50w -200v is connected across a 100v supply. The power consumed by the bulb  at present isA) 37.5wB) 25wC) 12.5wD) 10w

Answer» Power of bulb (P) = V^2/R

Where V is the voltage and R is the resistance of the bulb. Here Powe =50W when voltage = 200V.

So R =V^2/P=200^2/50=800ohm.

When supply voltage is 100V then

Power =100^2/800=12.5W


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