Alternating currents — AS & A Level Physics (9702) questions by topic
Alternating currents questions involve a bridge rectifier missing three diodes, comparing r.m.s. voltages, and defining the frequency of an alternating current, worth from 8 to 11 marks across 10 real questions from 2023 to 2024 papers, the narrowest year span in this A Level Physics set.
Draw, state and calculate lead the command words, with find and deduce also common: draw the missing diodes pointing the correct way, not guess a plausible arrangement. Submitting each attempt for instant marking flags a rectified voltage graph confused with a power-time graph, or a full time period used instead of the correct half-cycle interval, before both errors repeat.
What examiners look for
- A significant number of candidates offer no response at all to this type of question, and many weaker candidates draw graphs showing no rectification.
- Examiners note the difference between a rectified voltage-time graph and a power-time graph is not understood by many candidates.
- A common mistake is using the total time elapsed rather than the correct shorter time interval in a calculation.
- Reports flag candidates who correctly conclude r.m.s. voltages are equal but then struggle to articulate the reason adequately.
- Strong answers correctly deduce that all additional diodes in a rectifier must point the same way as the one already printed on the diagram.
May–June 2024, Paper 41
A circuit contains a power supply that provides a sinusoidal alternating input voltage VIN. There is an output voltage VOUT across a load resistor R, as shown in Fig. 7.1. The…
Answer this question and get it marked →May–June 2024, Paper 43
A circuit contains a power supply that provides a sinusoidal alternating input voltage VIN. There is an output voltage VOUT across a load resistor R, as shown in Fig. 7.1. The…
Answer this question and get it marked →October–November 2024, Paper 41
State what is meant by rectification of an alternating voltage.
Answer this question and get it marked →October–November 2024, Paper 42
State what is meant by the frequency of an alternating current.
Answer this question and get it marked →October–November 2024, Paper 43
State what is meant by rectification of an alternating voltage.
Answer this question and get it marked →May–June 2023, Paper 41
Part of an electric circuit is shown in Fig. 5.1. The circuit is used to produce half-wave rectification of an alternating voltage of potential difference (p.d.) V(IN). The output…
Answer this question and get it marked →May–June 2023, Paper 42
Four diodes are used in a bridge rectifier circuit to produce rectification of a sinusoidal a.c. input voltage V(IN). Fig. 7.1 shows part of the circuit, but three of the diodes…
Answer this question and get it marked →May–June 2023, Paper 43
Part of an electric circuit is shown in Fig. 5.1. The circuit is used to produce half-wave rectification of an alternating voltage of potential difference (p.d.) VIN. The output…
Answer this question and get it marked →October–November 2023, Paper 41
A varying current I passes through a resistor of resistance R in the circuit shown in Fig. 7.1. Fig. 7.2 shows the variation with time t of I. The current has magnitude 2I0 when…
Answer this question and get it marked →October–November 2023, Paper 43
A varying current I passes through a resistor of resistance R in the circuit shown in Fig. 7.1. Fig. 7.2 shows the variation with time t of I. The current has magnitude 2I0 when…
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