Alternating currentsAQA A-Level Physics: Mind map

Exam questions on Alternating currents

1. A heating element of resistance 46 Ω is connected to the UK mains supply, which has an rms voltage of 230 V and a frequency of 50 Hz. The supply voltage is sinusoidal.
   Explain why the mean power dissipated in the element is half of its maximum instantaneous power.2 marks
2. An oscilloscope is used to display a sinusoidal alternating voltage. The Y-gain is set to 2.0 V per division and the time-base to 5.0 ms per division. The trace has a peak-to-peak height of 5.2 divisions, and one complete cycle of the trace occupies 4.0 divisions horizontally.
   Calculate the rms voltage of the signal.2 marks
3. A signal generator supplies a sinusoidal alternating current of peak value 1.5 A and frequency 400 Hz to a resistor of resistance 12 Ω.
   Calculate the rms current and the mean power dissipated in the resistor.3 marks