Question

An alternating current of frequency 'f' is flowing in a circuit containing a resistance R and a choke L in series. The impedance of this circuit is

• A. $R+2\pi fL$
• B. $\sqrt{R^2+4{\pi }^2{f}^2{L}^2}$
• C. $\sqrt{R^2+L^2}$
• D. $\sqrt{R^2+2\pi fL}$

Answer 1

The correct option is B $\sqrt{R^2+4{\pi }^2{f}^2{L}^2}$

$Z=\sqrt{R^2+X_L^2},X_L=\omega L$ and $\omega =2\pi f$
$\therefore Z=\sqrt{R^2+4{\pi }^2{f}^2{L}^2}$