Question

An ac generator G with an adjustable frequency of oscillation is used in the circuit, as shown.
Current drawn from the ac source will be maximum if its angular frequency is-

• A. ${10}^5$ rad/s
• B. ${10}^4$ rad/s
• C. 5000 rad/s
• D. 500 rad/s

Answer 1

The correct option is C 5000 rad/s

$c=(3+4.5+2.5)\mu F$

$=10\mu F$

$L=L_1+L_2=4mH,R=100\Omega$

At resonance, $\omega =\frac{1}{\sqrt{LC}}=\frac{1}{\sqrt{4\times {10}^{-3}\times 10\times {10}^{-6}}}=\frac{1}{\sqrt{4\times {10}^{-8}}}$

$=\frac{1}{2}\times {10}^4=0.5\times {10}^4=5$kHz.