Question

An inductor and a resistor in series are connected to an AC supply of variable frequency. As the frequency of source is increased, the phase angle between current and potential difference across L will

• A. go on increasing
• B. go on decreasing
• C. first increase then decrease
• D. first decrease then increase

Answer 1

The correct option is A go on increasing

Solution:-

In the given circuit, Current flown will be equal to

$I=\frac{V_0}{\sqrt{R^2+{\omega }^2{L}^2}}\sin (\omega t-\varphi )$

where $V_0$ is peak value of input

$V=V_0\sin \omega t$

hence $\varphi$ is the phase difference i.e. given as

$\tan \varphi =\frac{\omega L}{R}$

Now as we increase frequency $\left(\omega \right)$ of source ; phase difference $\left(\varphi \right)$ also increases.