Question

A series LCR circuit with R = 22 $\Omega$, L = 1.5 H and C = 40 $\mu$ F is connected to a variable frequency 220 V ac supply. When the frequency of the supply equals the natural frequency of the circuit, what is the average power transferred to the circuit in one complete cycle?

• A. 2000 W
• B. 2200 W
• C. 2400 W
• D. 2500 W

Answer 1

Answer: (B)

2200 W

When the frequency of the supply equals to the natural frequency of circuit, resonance occurs.
$\therefore Z=R=22\Omega and{I}_{rms}=\frac{V_{rms}}{Z}=\frac{220}{22}=10A$
Average power transferred per cycle,
$P=V_{rms}{I}_{rms}cos{0}^{\circ }=220\times 10\times 1=2200W$