Electricity questions

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• AQA 7408 · June 2025 · Paper 1 · Q5 · 6 marks

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  Question 5.1 was answered correctly by nearly 70% of students. Incorrect rounding and giving the lost volts as the answer were common errors that did not get the mark. Some power of ten errors were also seen. Question 5.2 was answered correctly by the majority of students. A common mistake was not taking the reciprocal to find the resistance. Students who tried to use the emf equation rarely made much progress. Very few students obtained all three marks for question 5.3. Some used values from the earlier part of the question, despite being told that the modules in this question were © 2025 AQA different. It was clear that combining cells in series and parallel is a challenge for many students.

  Text version

  An electric-vehicle battery is a series of modules, each made from arrays of identical cells. One cell has emf 3.66 V, internal resistance 30.0 mOhm and maximum current 6.77 A.

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• AQA 7408 · June 2024 · Paper 1 · Q6 · 11 marks

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  This electricity question was set in the context of a thermistor circuit. The calculation in question 06.1 was completed successfully by nearly 90% of students. The multi-step calculation in question 06.2 produced a good range of marks and discriminated well. A surprisingly large number of students struggled to convert 22oC into kelvin. Many students used their answer to 06.1 as the resistance, despite the situation having changed. Many students had difficulty dealing with taking natural logs, believing that log (A÷B) = log A ÷ log B for example. The unit also proved to be challenging for many students. Those who understood that the arguments of a function such as ex are dimensionless spotted that B must have the same units as temperature. The problems of resistive heating in thermistors was tested in 06.3. Many students understood that the current would causing heating of the thermistor, but few could go on to explain the effect that this has on resistance. The best answers referred to issues of thermal runaway, although this was not required for full marks. A similar question to 06.4 was set on a recent paper. Despite this, few students were able to make the link between charge and energy, and current and pd. Students also had difficulty describing what they would do with the ammeters and voltmeters in their circuits.

  Text version

  A 6.5 V ideal battery, a thermistor between X and Y, and a variable resistor between Y and Z are connected in series. At 22 degrees C the thermistor resistance is 350 ohm and the circuit current is 12 mA.

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• AQA 7408 · June 2024 · Paper 3A · Q1 · 15 marks

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  We expect students to have used a micrometer screw gauge and in 01.2 87% correctly indicated that the reading shown was 6.72 mm. In 01.3 they were told to state and explain how the micrometer should be closed; many could ‘state’ what they should do but then overlooked the ‘explain’ part. In 01.4 the working could be hard to follow but usually saw one of several acceptable approaches, including some novel potential-divider solutions. Having been required to show that R was about 0.5 Ω, a 2 sf final answer 0.51 would have been fine, otherwise only 0.512 and 0.5117 were accepted. Over 70% scored both marks. Parts 01.5 and 01.6 proved very accessible. A clear majority correctly identified nichrome by matching up their 01.5 result with a value of resistance per metre from Table 1, deducing the wire diameter and completing the resistivity calculation successfully. Some imported a power of ten error from their 01.5 calculation which led to them identifying copper. Others simply ignored powers of ten altogether and just tried matching up numbers so a resistance per metre of 1.68 became 0.168 and led to alumel. Part 01.7 was not well answered. We wanted students to compare the L bars and the R bars separately. A simple statement that the L bars were the same was accepted but we wanted a quantitative comparison of the R bars. Some ignored the L bars and others penalised themselves by not mentioning error bars at all. A few compared the bars at the first point with those at the fourth point (and not the fifth point as specified). Most knew how to determine the uncertainty in a gradient but the use of error bars in drawing the lines of maximum or minimum gradient was poorly explained. Although we expected students to explain how to determine the absolute uncertainty, we allowed them to give correct expressions for fractional or percentage uncertainty.

  Text version

  A student investigates the resistivity of a wire. The wire diameter is measured with a micrometer. A circuit contains a 1.2 ohm fixed resistor in series with the test wire and a dc supply; voltmeters measure the potential differences across the fixed resistor and across the test wire. The student measures the resistance R for several lengths L of wire.

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• AQA 7408 · June 2024 · Paper 3A · Q2 · 15 marks

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  In 02.1 most wrote something sensible about the display, as the question said they should, although a few said that the selector switch in Figure 6 was shown set to range C. In 02.2 65% got both marks and only a few did not use logs to base 10 or substitute 2840 correctly. However, some solutions were overlong, extending beyond the usual answer space. In 02.3 many said they would obtain EV and x data from Figure 7 and show that these gave similar values of EV × x2. We wanted these data to be from more than two points but only a few thought to mention this detail. We didn’t allow the use of ‘multiple points’. An alternative approach was to plot EV against x2 or plot log EV against log x and this could get full credit as long as the expected outcome was explained for each graph. The idea behind 02.3 was developed in 02.4 and many calculated a suitable value of x when EV = 130 lx. Some penalised themselves by rounding their final answer to 630 or 640 mm. In 02.5 most correctly supplied 1645 and 1.73 then used information from their completed Table 3 to justify why range B should be used to determine R. Some tried the idea that resolution of range B was superior but were unsure whether they should say that the resolution was ‘smaller’, ‘greater’ (we accepted either) or ‘better’ (we rejected this). Students are well aware of what a control variable is, but they are not always able to identify suitable examples. In 02.6 they often made generic suggestions such as temperature or the length of the connecting wires, but we wanted things that, if changed, would have a more obvious impact such as background illumination, lamp brightness or slide thickness. Most students can find the unknowns in decay problems. In 02.7 about half knew that µ would be found by calculating the negative reciprocal of the gradient of an ln EV against N graph. A handful correctly explained how to obtain µ using a log EV against N graph. In 02.8, once again about half correctly deduced that eight slides would be the minimum needed to reduce EV by 50%. Some tried trial and improvement, but credit depended on showing that N = 7 did not work while N = 8 did. A common error was to use EV = 0.5 which led to N = 74.3 but we allowed one mark if this was then rounded to 75.

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  A student investigates an LDR illuminated by a lamp. An ohmmeter connected to the LDR displays 02.84. Its selectable ranges are: A, 000.1 to 199.9 ohm; B, 0001 to 1999 ohm; C, 00.01 to 19.99 kohm; D, 000.1 to 199.9 kohm; E, 0.001 to 1.999 Mohm. The lamp-LDR separation is x and the illuminance at the LDR is EV.

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• AQA 7408 · June 2023 · Paper 1 · Q3 · 11 marks

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  [03.4] There were five marking points for a maximum of four marks. The mark scheme was designed to reward partial credit for those students who made errors. Most students had some problem understanding what was happening at position Q on Figure 5. The question produced a very good spread of marks, with over 70% of students picking up at least one.

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  A 3.00 V cell with internal resistance r drives a 125 ohm conducting track AB in series. A sliding contact C taps the track, and an ideal voltmeter measures the pd from A to C. At C = B it measures the terminal pd across the full 125 ohm track.

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• AQA 7408 · June 2023 · Paper 3A · Q2 · 16 marks

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  [02.3] This part was well answered and many recognised that they should calculate the minimum current or the minimum potential difference when X was set to maximum resistance. Better-performing students often went on to compare these results with relevant data in Figure 4 to justify their rejection of circuit 1. A few proved circuit 1 was unsuitable by comparing 2.3  with the resistance calculated using the first or second points on Figure 4. We wanted them to say that the potential divider could vary the pd from 0 to 12 V so circuit 2 could produce the data in Figure 4, but this detail eluded most. Some tried to calculate the maximum current in X for circuit 1 but mistakenly used 2.3  in their calculation. 02.4 and 02.5 Although most found 02.4 and 02.5 straightforward, some penalised themselves in 02.4 by inconsistent s.f. in the data or, in 02.5, by failing to recognise the non-linear trend in their plotted points. It was surprising to find how many did not draw any best-fit line.

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  A data logger records the current-voltage characteristic of filament lamp L at 2.5 samples per second while V increases steadily. Representative data include (V, I): (3.30 V, 1.07 A), (5.17 V, 1.32 A), (7.69 V, 1.59 A), (9.58 V, 1.77 A), (11.47 V, 1.94 A). The first plotted current is about 0.36 A, and the characteristic extends smoothly to about I = 1.98 A at 12 V.

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• AQA 7408 · June 2022 · Paper 1 · Q4 · 11 marks

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  04.1 was very straightforward. This was a ‘show that’ question and students failed to gain marks when they did not make it clear what they were doing by setting out the equation and substituting the data. 04.2 was much more challenging. There were several creditable approaches, with much opportunity in the mark scheme for partial credit. This was only given when it was clear what the student was doing. 04.3 was much more accessible. Most students were able to give a complete answer with only powers of ten errors causing problems for some in the final mark. Examiners expected 04.4 to be answered very well. However, a significant number of students could not get beyond the idea that the resistance of the variable resistor increased. At A-level, students are expected to be able to answer an electricity problem of this kind without a circuit diagram, but many students were unable to work out what was going on without it. A major difference between problems on electricity at A-level and GCSE is the consideration of internal resistance. Correct answers for 04.5 were extremely rare, and answers to this question demonstrated many of the misconceptions students have about electricity. A significant number of students have clearly not moved beyond the idea that ‘electricity follows the easiest path’. Many answers to this question were confused, ambiguous and contradictory.

  Text version

  A 6.2 V, 4.5 W lamp is connected in parallel with a 12 ohm resistor. This parallel combination is connected to a battery with internal resistance 2.5 ohm. A separate 5.0 m resistance wire of diameter 0.19 mm has resistance 9.0 ohm and is used as a variable resistor.

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• AQA 7408 · June 2022 · Paper 3A · Q3 · 11 marks

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  This question was about finding the resistivity of conductive putty and addressed ideas behind required practical activity 5. In 03.1, about two-thirds of students identified that use of callipers could deform the putty or cause the diameter reading to be reduced. Although a ‘show that’ question, 03.2 was very similar to 03.3 in November 2021. More than half earned both marks by producing an answer that rounded to 2.37%. Nearly 30% scored full credit in 03.3. Some penalised themselves by not combining the percentage uncertainties correctly, but could still get credit for determining a recognisable volume or for substituting their values into a calculation of the uncertainty in the volume. There were isolated cases where maximum and minimum volumes were calculated based on the extreme values of d and L. This proved to be a viable alternative to the anticipated method and could earn full credit. In 03.4 students were back on familiar territory and (mostly) drew an acceptable line, measured the gradient, and did the required calculation to find the resistivity. A common error was to miss the multiplier with the label on the L2 axis leading to 10−5 on the answer line. The margin of error with the numerical value was small so truncation to 2 sf was ill-advised. Over half of the students scored at least 3 marks.

  Text version

  Conductive putty can easily be formed into different shapes to investigate the effect of shape on electrical resistance.

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• AQA 7408 · November 2021 · Paper 1 · Q6 · 5 marks

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  Students often have difficulty with electricity questions at this level. The added complication of a log-log graph proved to be beyond the experience or understanding of many students. Section B Several of the multiple-choice questions proved to be extremely difficult. In particular, questions 20, 27 and 29 were answered correctly by fewer than 30% of the students. In question 20 more students opted for B and for C than for the correct answer (D), indicating a lack of familiarity with scale diagrams. In question 27 the most popular answer was B, indicating the difficulties students have with combining resistors, and the second most popular was C, suggesting that students did not understand the difference between open and short circuits. The most popular answer to question 18 was D, probably because the students did not spot that this was a stationary, rather than progressive, wave. The most accessible questions were 10 and 16, both of which were answered correctly by over 70% of the students. Concluding Remarks The standard, range and style of questions used in this paper were similar to those used in previous series. The mathematical difficulty and Assessment Objective (AO) coverage was also very similar. It was clear that many students were unable to make much progress with the questions requiring them to choose their own method, or reach a judgement or conclusion. These are the questions that are designed to assess AO3. Whilst this has been true in previous series, the evidence for it was even stronger here. Generally the questions on particles were answered well. Other topics which had a strong link to GCSE content were also answered confidently, but often at too low a level to obtain many marks. The poor performance on the question on circular motion and the electricity question indicated a lack of knowledge or understanding in these areas.

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  An LDR and 10 kohm resistor are in series across an ideal 5.0 V supply, with sensor voltage V_s across the LDR. From its log-log graph, LDR resistance is about 93 kohm at 4.0 lux and 300 kohm at 1.0 lux. The alarm sounds if V_s changes by more than 25% of supply emf.

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• AQA 7408 · November 2021 · Paper 3A · Q2 · 10 marks

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  This question was about the light emitted from different LEDs but included general ideas about the use of diffraction gratings, as used in Required Practical Activity 2. In question 02.1 students had to make an easy read-off from Figure 3 and then apply an equation available in the Formulae and Data booklet. Despite the low demand of the question, fewer than a third of the students were able to obtain full credit. Question 02.2 is one of several in the paper where those suggesting simple practically-based explanations were most likely to score. About 40% of students mentioned some relevant characteristic of the 5th maximum to score the available mark. It was clear that some did not understand what we wanted them to do in question 02.3 and many showed no evidence of working on Figure 4. In question 02.4 only 3% of the students successfully used data about both LEDs; some engineered an answer that duplicated the value in the Formulae and Data booklet. All students realised that c is the speed of light but not all recognised that e is the electronic charge and used 2.718 in their calculation. Question 02.5 was the least accessible part and only 10% of students used Figure 4 to determine the voltage drop across the LED before going on to deduce the minimum value of R.

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  Green LED LG and red LED LR have equal peak intensity. Their spectral peaks are about 565 nm and 635 nm. Extrapolated activation voltage for LG is 2.00 V; the LR current-voltage graph has a linear high-current section and at 21.0 mA its forward voltage is 2.01 V.

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• AQA 7408 · November 2021 · Paper 3A · Q3 · 19 marks

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  This question was set in the context of Required Practical Activity 9. In question 03.1 more students chose the distractor 13.5 than the correct value of 2.7, suggesting that many did not appreciate the distinction between ‘more sensitive’ and ‘less sensitive’. Question 03.2 is a question used in an earlier series. Some students improvised answers such as ‘the mirror was used to illuminate the scale to eliminate human error’. Only 10% could supply a completely correct answer. Question 03.3 was poorly answered in comparison with similar examples in previous papers, with many failing to halve the range before calculating the percentage uncertainty. In question 03.5 most found that the space provided was adequate for them to complete their answer; those who needed supplementary pages usually included information already provided in the question. Many could suggest something sensible about meter protection, checking that C was discharged being the most popular idea. Some recognised the advantage of timing for longer but suggested impractical ideas such as ‘measure the time for C to fully discharge’ or ‘add a resistor to the circuit’. Few could state how they would test for any relationship between range and time constant. Weaker students wrote that they would check whether the half life was 2.5 s. More than half were able to score one mark in question 03.6 by making at least one relevant observation about the values of V in Table 2, although finding an explanation to back up their observation was a harder proposition. In question 03.7 at least 30% knew how to find the voltmeter resistance (as per page 116 of the physics practical handbook). However, half of the students, despite often obtaining relevant data from Figure 8, then failed to make enough progress to score. In question 03.8 it was surprising to find that many, having correctly read relevant information from Figure 8, then attempted to calculate the current using 3 10 10 16 ln × V . Concluding Remarks The demands of this paper were no greater than in 2019. Besides demonstrating knowledge and understanding of the required practical activities, students must show that they can apply their core understanding of practical work in new and unfamiliar contexts. Some will not have seen an analogue meter and we would not expect any to have heard about the dead time of a radiation detector, but this would not have affected their ability to tackle the questions we set. Question 1 revisited Required Practical Activity 12 which featured in 2019 and this will have benefited those who looked at past papers and schemes. Specification coverage of theory leading up to Required Practical Activities 12 and 9 (see question 3) would normally take place later in the course, so both of these should have been fresh in students’ memory. However this assumes that students will have had uninterrupted study and this clearly will not be true in every case. The impression gained was that students felt more comfortable writing about capacitor discharge than about the inverse-square law. Where possible they should be given direct experience of using equipment relevant in each of the practical activities, including the safe manipulation of a sealed radioactive source. As might be expected, work at grade A was in very short supply, but a handful of capable students submitted answers and some of them found innovative variations on the expected approaches to question 03.7. At the other end of the spectrum we saw evidence of calculators set to read angles in radians (in question 02.1) and misguided attempts to use the Boltzmann constant (in question 01.3). Aside from questions 01.2, 01.3, 02.1 and 03.3, students at about the E boundary found marks difficult to obtain. Some of the work seen in questions 01.1 and 03.2 show that, while students know about parallax error, they are not always aware of techniques used to limit its effect. This is an area we will continue to test and the best way to acquire knowledge of such techniques is by direct practical experience. Work seen in question 01.4 suggests that some students wrongly assume that sealed sources emit γ radiation only through the open end of the source. Students should be made aware of the expectations behind the different command words used in the questions. When we use ‘Explain’ we expect a reasoned justification to be included and when, as in question 01.3, they are basing a decision based on a numerical outcome, the justification should be quantitative, eg a percentage-difference calculation. There is always scope in this paper to test the Maths Skills listed in section 6 of the specification. Question 01.6 exposed weak understanding about the use of logarithmic plots to test power law variations (MS3.11). Relevant opportunities for skills development are identified in the main body of the specification.

  Text version

  A dual-range analogue voltmeter has 3 V and 15 V ranges. On the 3 V scale its uncorrected zero is +0.3 V. A mirror runs along the scale. After zero correction, an unknown capacitor discharges through the meter. For the later 820 microF discharge, Figure 8 is a straight best-fit plot of ln(V / 1 V) against t passing approximately through (0 s,2.64) and (28 s,0.50).

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• AQA 7408 · November 2020 · Paper 3A · Q3 · 17 marks

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  This question was about assessed practical 6. Physics errors seen in the diagrams for 03.1 included some that were below the level of a good GCSE student. Some were drawn freehand or contained gaps. Only 40% obtained the mark for this part. In 03.2, credit for describing the procedure was withheld when the voltmeter was connected across P or there was a suggestion that Q had been calibrated. Descriptions of the processing were generally consistent with the version in the physics handbook and about 30% were able to get full credit. However, it was disappointing that 25% scored zero and a further 11% did not attempt this very accessible question. It was rare to find completely successful answers to the sequence from 03.3 to 03.5. In the first part we hoped to see (22  the result of a gradient calculation) but full credit could be earned by outlining a simultaneous-equation approach. The only way to show that the current was about 0.25 A was by recognising that n = 4 and then using Figure 12. In 03.5, students could often deduce the e.m.f. and the internal resistance but less than 10% scored all 4 marks. The rubric states that answers to 1 sf will not (normally) be acceptable but it was common to find the internal resistance given as 0.9 Ω. In 03.6, it seemed that many did not recognise the impossibility of distributing data evenly across the gap between n = 1 and n = 14. Presumably this was why so many suggested the combination of n = 4, 7 and 10. Others suggested using non-integer values for n. In 03.7, about 30% scored 1 mark, usually by deducing that the use of 27 Ω resistors would decrease the gradient. Only about 5% recognised that this would require both points to move to the right of the graph. Concluding Remarks Each marking point proved accessible except 02.5 and the third mark in 03.7. Despite having similar demands to the 2019 edition, the 2020 paper proved less discriminating, probably because stronger students were under-represented. Students generally engaged with the command word although there is still a reluctance to ‘annotate’, e.g. where we ask them to put detail on a printed Figure. They did not always pay attention to the entirety of the command sentence, e.g. in 02.6 and 03.4 some clearly missed the instruction to use a particular Figure to make their deduction. The mathematical skills employed by the students were usually sound and at least as good as in a typical series. Most recognise and can exploit the y = mx + c idea. Working was usually transparent and faulty manipulation was rare. There is evidence that teachers are not examining the ‘dark corners’ of Section 6 of the specification. Many students have a blind spot with log-log plots and with order of magnitude calculations. Candidates are sometimes unsuccessful even with AO1 questions. Review of previous mark schemes would remedy many of these shortcomings. Questions testing the AO2 criteria are also a mixed bag: in 01.4 the uncertainty calculations were often done well but the graph scaling/plotting in 01.6 was patchy. When the information is out in the open and the context is familiar as in 03.5, students can make progress with AO3 questions, but the novel scenarios such as in 03.6 defeat most.

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  Experiments determine the emf epsilon and internal resistance r of a power supply. One method varies external resistance and measures terminal pd V and current I. Another connects n identical 22 ohm resistors in parallel, for which 22/n = epsilon/I - r, and plots reciprocal variables.

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• AQA 7408 · June 2019 · Paper 1 · Q7 · 4 marks

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  [7.1] The determination of the internal resistance and emf of a cell is a practical experiment students are required to undertake when studying this specification. The reference to a practical circuit should have alerted students to assume that the internal resistance of the cell must be taken into account. Students who were sufficiently familiar with the phenomenon were unlikely to have much difficulty with this question. However, big gaps in the knowledge and understanding of electricity were seen in the answers given by many students. Most students are familiar with the idea of increasing current and potential difference (p.d.) through V = IR. However, presented with the apparent paradox of increasing current and decreasing p.d., many students could not cope. It should be stressed that students should assume a cell has internal resistance unless otherwise stated explicitly in the question. It is unlikely that a resistance symbol will be added to the circuit diagram to indicate the presence of internal resistance. Those students who gained one mark for their answer usually did so by stating that the current through the lamp increased.

  Text version

  Cell with internal resistance drives lamp through variable resistor; voltmeter measures terminal pd.

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• AQA 7408 · June 2018 · Paper 1 · Q4 · 12 marks

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  [04.1] The problem that has been discussed in question 03.4 was evident in this question too but there was a high proportion of correct solutions (58.9% scored full marks) to this relatively familiar problem.

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  A9.0 V temperature monitor has a250 ohm series resistor and a parallel output branch containing a750 ohm room-temperature thermistor and resistor R. The250 ohm resistor is50 turns around an8.0 mm cylinder, wire resistivity4.2 x10^-7 ohm m. Desired room output is5.0 V.

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• AQA 7408 · June 2018 · Paper 3A · Q1 · 19 marks

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  [01.4] The first row of Table 1 attracted the most correct responses and thereafter things got patchier. Examiners needed to see correct responses in both row 3 and row 4 to earn the third marking point; this proved beyond all but the most able, with only 11.4% obtaining full credit.

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  A practical uses a metre ruler pivoted at1.0 cm and supported by a prism on a zeroed balance at30.0 cm; with the horizontal ruler alone the balance reads214.66 g. In the side-view diagram, terminal P is at the left end and Q at the right end of a wire along the ruler. The supply makes conventional current flow P-to-Q, rightwards across a5.0 cm horizontal magnetic-field region at the85-90 cm marks. The straight M-against-I graph has gradient -0.28 g A^-1.

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• AQA 7408 · June 2017 · Paper 1 · Q4 · 9 marks

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  A quite detailed circuit analysis was required for this question and some very impressive answers were seen. In question 04.1 the commonest reason for losing a mark was a failure to indicate that the gradient of the graph gave the negative value of internal resistance. Identifying which circuit would be suitable to power the road sign involved a detailed analysis; while over a third of students were able to do this successfully, a significant proportion of these then failed to score the conclusion mark because they did not state clearly that the circuit in Figure 6 was suitable because it provided a current greater than 75 mA. Less able students struggled when dealing with the series and parallel combination of cells. Of those who could correctly identify the combined internal resistance as 12 Ω, few were then able to give the combined emf as 1.4 V. The analysis of the circuit in Figure 5 was much more straightforward and nearly 80% of students were able to do this. There are of course alternative approaches to the analysis and any correct method was given full credit. Question 04.3 involved an efficiency calculation. A large number of students were able to calculate the useful power output but a surprising number did not deal with the 4.0% efficiency correctly. It was quite common to see the input power multiplied by 0.96 rather than divided by 0.04. There were also, as is frequently the case, power of ten errors when dealing with the surface area.

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  A solar cell has terminal-pd/current line V=0.70-8.0I, with V in volts and I in amperes. A road-sign lamp needs at least 75 mA and has resistance 6.0 ohm at that current. Circuit 5 uses one cell. Circuit 6 uses two identical cells in parallel, in series with one further identical cell. The cell supply has total illuminated area 32 cm^2 and converts solar to useful electrical energy with 4.0% efficiency.

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