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. p H
• D. $\frac{2\sqrt{3}}{\pi}$H

Answer 1

Answer: (D)

$\frac{2\sqrt{3}}{\pi}$H

Answer 2

R =$\frac{(120)^{2}}{60}$= 240 W we require i = 0.5 A

or |Z| = 480 W

X_L =$\sqrt{480^{2} - 240^{2}}$= 240$\sqrt{3}$W

L =$\frac{240\sqrt{3}}{60 \times 2\pi}$=$\frac{2.\sqrt{3}}{\pi}$H