Question

An arc lamp requires a direct current of 10A at 80V to function. If it is connected to a 220V (rms), 50 Hz AC supply, the series inductor needed for it to work is close to:

• A. 80H
• B. 0.08H
• C. 0.044H
• D. 0.065H

Answer 1

The correct option is D 0.065H

Resistance of lamp by ohm's law,

$R=\frac{V}{I}=\frac{80}{10}=8\Omega$

When inductor is connected in series and source is applied,

$V=IZ$

$V=I\sqrt{R^2+(\omega L{)}^2}$

Given, $I=10A$ for lamp to work,

$\therefore 220=10\sqrt{8^2+(2\times \pi \times 50\times L{)}^2}$

Solving,

$L=0.0648H$