An alternating current (a.c.) power supply is connected in series with a resistor of resistance RRR. A cathode-ray oscilloscope (c.r.o.) is connected in parallel with the resistor.
Initially, without any diode in the circuit, the trace on the c.r.o. shows a sinusoidal alternating voltage with a peak value of V0=12 VV_0 = 12\text{ V}V0=12 V and a period of 20 ms20\text{ ms}20 ms.
An ideal diode is now inserted in series with the power supply and the resistor.
Describe the trace now seen on the c.r.o. screen over one complete cycle of 20 ms20\text{ ms}20 ms.
State the name of the process that the voltage has undergone.
State and explain how the average power dissipated by the resistor changes after the diode is inserted, and calculate the ratio:
Average power with the diodeAverage power without the diode \frac{\text{Average power with the diode}}{\text{Average power without the diode}} Average power without the diodeAverage power with the diode136 exam-style questions on CIE IGCSE Physics 4.3 Electric circuits, covering 4.3.1a Circuit diagrams and circuit components, 4.3.2a Series circuits, 4.3.2b Parallel circuits, 4.3.2c Current and potential difference in circuits, 4.3.2d Combined resistance of resistors in parallel, and 4.3.3 Action and use of circuit components. Each one has a worked solution and a mark scheme showing where the marks go.