Question

A 60 W/120 V bulb is connected to a 240/60 Hz supply with an inductance in series. Find the value of inductance so that bulb gets correct voltage.

• A. $\frac{2.3}{\pi }$ H
• B. $2\sqrt{3}$ H
• C. $\pi$ H
• D. $\frac{2\sqrt{3}}{\pi }$H

Answer 1

The correct option is D $\frac{2\sqrt{3}}{\pi }$H

$R=\frac{(120{)}^2}{60}=240\Omega$ we required $I=0.5$ A

or $|Z|=480$ $\Omega$

$X_L=\sqrt{{480}^2-{240}^2}=240\sqrt{3}\Omega$
$L=\frac{240\sqrt{3}}{60\times 2\pi }=\frac{2\sqrt{3}}{\pi }H$