Question

A coil of $200 \Omega$ resistance and $1 H$ inductance is connected to an a.c. source of frequency $\frac{100}{\pi}Hz$, phase angle between potential and current will be:

• A. $30^{\circ}$
• B. $45^{\circ}$
• C. $60^{\circ}$
• D. $90^{\circ}$

Answer 1

Answer: (B)

$\cos \phi =\frac{R}{Z}=\frac{R}{\sqrt{(R)^{2}+\omega^{2} L^{2}}}$
$=\frac{200}{\sqrt{200^{2}+(200)^{2} \times(1)^{2}}}$
$\cos \phi=\frac{1}{\sqrt{2}} =\phi=45^{\circ}$