Question 464: Current Electricity

Question

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 _____________ $$\Omega$$.

Accepted Answer

Power, $$P = {{{V^2}} \over {{R_B}}}$$
$${R_B} = {{{V^2}} \over P} = {{100 	imes 100} \over {200}}$$
$${R_B} = 50\Omega $$
To produce same power, same voltage (i.e. 100 V) should be across the bulb.
Hence, R = R
B
R = 50 $$\Omega$$

Current Electricity

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 _____________ $\Omega$.

Choose the correct answer: