In India electricity is supplied for domestic use at $220 \mathrm{~V}$. It is supplied at $110 \mathrm{~V}$…
In India electricity is supplied for domestic use at $220 \mathrm{~V}$. It is supplied at $110 \mathrm{~V}$ in USA. If the resistance of a $60 \mathrm{~W}$ bulb for use in India is $R$, the resistance of a $60 \mathrm{~W}$ bulb for use in USA will be:
$R$
$2 R$
$\frac{R}{4}$
$\frac{R}{2}$
Solution
In India, $P_1=\frac{(220)^2}{R}$
In USA $\quad P_V=\frac{(110)^2}{R_0}$
As $\quad P_1=P_V$
$\begin{aligned}
& \Rightarrow \quad \frac{(220)^2}{R}=\frac{(110)^2}{R_V} \\
& \therefore R_V=\frac{110 \times 110}{220 \times 220} \Rightarrow f v=\frac{R}{4}
\end{aligned}$