Question

A $100$ watt bulb working on $200$ volt has resistance $R$ and $a \,200$ watt bulb working on $100$ volt has resistance $S$. If the $R/S$ is $\frac{8}{x}$. Find the value of $x$.

Answer 1

$P = V^2/R$
$\Rightarrow R = V^2/P \times 10^4 / 100 = 400 \,\Omega$
$S = 10^4/200 = 0.5 \times 10^2 = 50\, \Omega$
$R/S = 8$