A resistor of 63 ohms is connected to a sinusoidal source with a peak voltage of 74 V. What is the average power dissipated?

• A. 53.2 W
• B. 19.5 W
• C. 66.8 W
• D. 43.46 W

Answer: (D)

The average power in a resistor fed by AC depends on the RMS voltage: P_avg = V_rms^2 / R. For a sinusoidal source, V_rms is the peak voltage divided by √2. With a peak of 74 V, V_rms^2 = (74^2)/2 = 5476/2 = 2738. Then P_avg = 2738 / 63 ≈ 43.46 W. So the power dissipated is about 43.46 watts. Using peak voltage directly would give a much higher value, which isn’t correct for average power in an AC circuit.