Question

Assertion :In an $L-R$ series circuit in $AC$, current in the circuit will decrease with increase in frequency. Reason: Phase difference between current function and voltage function will increase with increase in frequency.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

$I=\frac{V}{Z}=\frac{V}{\sqrt{R^2+X_L^2}}$

$=\frac{V}{\sqrt{R^2+(2\pi fL{)}^2}}$

With increase in frequency, $I$ will decrease.

$\tan \varphi =\frac{X_L}{R}=\frac{2\pi fL}{R}$

With increase in frequency $\tan \varphi$ and therefore $\varphi$ will increase.