20. Consider a purely resistive heater connected to an AC power source (rms
voltage 120 V, frequency 60 Hz) with an average heating power of 1 kW. If an
inductor is connected in series with the heater, causing the average heating
power to drop to 1/4 of its original value, what is the phase angle between the
voltage and the current? (A) 15° (B) 30° (C) 45° (D) 60° (E) 90°