Question

A bulb of $100\text{W}-250\text{V}$ is connected to $250\text{V}$ mains. If another similar bulb is connected to it in series, the total power consumption(in $\text{W}$) is

Answer 1

Given $P=100\text{W};V=250\text{V}$

$R=\frac{V^2}{P}=\frac{250\times 250}{100}=625\Omega$

Power of one of the bulbs,

$P_1=\frac{V{{}_1}^2}{R}=\frac{(125{)}^2}{625}=\frac{125\times 125}{625}$

$P_1=25\text{W}$

$\begin{array}{c}{P}_1=P_2\end{array}$

Total power consumed by both the bulbs is, $P^{\prime }=2P_1=2\times 25=50\text{W}$