Question

A series L-C-R circuit with R = 20 $\Omega$ L = 1.5 H and C = 35$\mu$ F is connected to a variable frequency 200 V ac supply. When the frequency of the supply equals the natural frequency of the circuit, the average power transferred to the circuit in one complete cycle is

• A. 0.5 KW
• B. 1.0 KW
• C. 2.0 KW
• D. 4.0 KW

Answer 1

The correct option is C 2.0 KW

$P_{av}=V_{rms}{I}_{rms}cos\Phi$
$\Phi =0\left(resonancecondition\right)$
$hence,P_{av}=\frac{V_r^{2}ms}{R}$
$=\frac{200\times 200}{20}=2000$
2KW.