Question

An electric bulb marked $40W-220V$ is connected with an electric supply of $110v$. Its elctric power is

• A. $100W$
• B. $40W$
• C. $20W$
• D. $10W$

Answer 1

The correct option is D $10W$

Formula,

$P=\frac{V^2}{R}$

$\to R=\frac{V^2}{P}$

$=\frac{{220}^2}{40}$

$=1210\Omega$

$P=\frac{V^2}{R}$

$=\frac{{110}^2}{1210}$

$=10W$