AQA A Level Physics
AQA A Level Physics 3.13 Electronics (Option E) Exam Questions
Free AQA A Level Physics exam questions for 3.13 Electronics (Option E), with a mark scheme for every pack. Covers MOSFETs, zener diodes, photodiodes, Hall effect sensors, capacitor and LC circuits, op-amps, logic gates, counters, ADCs and data communication systems.
3.13 Electronics (Option E) exam questions
3 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About AQA A Level Physics 3.13 Electronics (Option E)
Electronics is optional topic 3.13 in AQA A Level Physics and is assessed in Section B of Paper 3 if your school chooses it. It covers discrete semiconductor devices such as MOSFETs, zener diodes, photodiodes and Hall effect sensors, analogue and digital signals, analogue signal processing with LC resonant filters and operational amplifiers, digital signal processing with logic gates and sequential circuits, capacitor timing circuits, data conversion, and data communication systems (3.13.6) including modulation, multiplexing and transmission media. It extends ideas from electricity, capacitance and waves in Papers 1 and 2. Examiners test op-amp gain calculations, resonance frequency, truth tables and explaining how a system transmits information.
What you need to know
- Semiconductor devices An n-channel enhancement MOSFET switches on above its gate threshold voltage and has a very high input resistance. A zener diode in reverse breakdown with a series resistor gives a fixed reference voltage. Photodiodes and Hall effect sensors (output pd proportional to B) act as sensors.
- Capacitor and LC circuits RC networks set timing in monostable and astable circuits, with the time constant RC controlling pulse length. An LC circuit resonates at f0 = 1 / (2 pi square root of (LC)), used to select frequencies; the Q factor is f0 divided by bandwidth.
- Operational amplifiers An ideal op-amp has very high open loop gain and input resistance. As a comparator the output saturates depending on which input is higher. Inverting amplifier gain = -Rf/Rin; non-inverting gain = 1 + Rf/R1; know summing and difference amplifiers and the gain-bandwidth product.
- Digital processing Know truth tables and Boolean algebra for NOT, AND, OR, NAND, NOR and XOR gates, combinational logic, and sequential logic such as D-type flip-flops, counters and astables used as clocks.
- Analogue and digital signals Digital signals resist noise because they can be regenerated. An ADC samples the signal; the sampling rate must be at least twice the highest frequency (Nyquist), and resolution depends on the number of bits. Bit rate = samples per second x bits per sample.
- 3.13.6 Data communication A system has a source, modulator, transmitter, transmission path, receiver, demodulator and output. Compare AM and FM, bandwidth, and transmission media: copper cable, optical fibre and free space. Time division multiplexing lets several signals share one channel.
Common mistakes in 3.13 Electronics (Option E)
- Forgetting the minus sign for an inverting amplifier. The output is inverted, so a positive input gives a negative output.
- Expecting an op-amp output to exceed its supply. The output saturates just below the supply rails.
- Sampling at the highest signal frequency. The sampling rate must be at least twice the highest frequency to avoid aliasing.
- Connecting a zener diode forward biased as a voltage reference. It must be reverse biased, beyond breakdown, with a series resistor to limit current.
- Using the wrong units in the LC resonance formula. Convert mH and nF into H and F before calculating.
Try three 3.13 Electronics (Option E) exam-style questions
1. An LC circuit has an inductance of 10 mH and a capacitance of 100 nF. Calculate its resonant frequency. (2 marks)
Show the mark scheme answer
f0 = 1 / (2 pi square root of (10 x 10^-3 x 100 x 10^-9)); = 1 / (2 pi x 3.16 x 10^-5) = 5.0 x 10^3 Hz.
2. An inverting amplifier has Rin = 10 kilohms and Rf = 100 kilohms with a supply of plus and minus 15 V. Calculate the output for inputs of 0.20 V and 2.0 V. (3 marks)
Show the mark scheme answer
Gain = -Rf/Rin = -10; for 0.20 V the output is -2.0 V; for 2.0 V the ideal output would be -20 V but it saturates at about -15 V.
3. Explain why digital signals are less affected by noise than analogue signals. (3 marks)
Show the mark scheme answer
Noise adds random variations to the signal during transmission; a digital signal has only two levels so the receiver can still identify each bit; the signal can be regenerated at repeaters, removing the noise, whereas amplifying an analogue signal amplifies the noise too.
3.13 Electronics (Option E) FAQs
What does AQA A Level Physics 3.13 Electronics cover?
It covers semiconductor devices, capacitor and LC circuits, operational amplifiers, logic gates and sequential circuits, analogue to digital conversion and data communication systems.
Which paper is the Electronics option examined in?
If your school takes this option, it is assessed in Section B of Paper 3, after the practical skills section.
What should I focus on when revising Electronics?
Practise op-amp gain calculations including saturation, LC resonance and bit rate calculations, and build truth tables for combinations of gates. Learn the block diagram of a communication system and the role of each part.
