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 + 2πfL
• 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

Answer: (B)

$\sqrt{R^{2} + 4\pi^{2}f^{2}L^{2}}$

Answer 2

$Z = \sqrt{R^{2} + X_{L}^{2}},\mspace{6mu}\mspace{6mu} X_{L} = \omega L$ and $\omega = 2\pi f$

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