Resistance and resistivity: past paper questions
Real questions on resistance and resistivity
The newest 20 of 205 written questions. Open one to see it on the real paper.
- 9702/21 · October/November 2025 · Q5b(i)[2]
The thermistor has resistance R 0 at a temperature of 0 °C. On Fig. 5.2, sketch a possible variation of the resistance of the thermistor with temperature between 0 °C and 100 °C. R 0 0 0 temperature / °C 100 resistance
See it on the paper → - 9702/21 · October/November 2025 · Q5b(ii)[3]
With reference to the current in the cell, explain why the current in resistor R decreases with increasing temperature of the thermistor.
See it on the paper → - 9702/21 · October/November 2025 · Q5c(ii)[2]
the resistance of the thermistor. (ii) resistance = Ω
See it on the paper → - 9702/23 · October/November 2025 · Q3b(i)[1]
State an expression, in terms of some or all of L, A, E and ρ, for the resistance R 0 of the wire. R 0 = (b) (i)
See it on the paper → - 9702/23 · October/November 2025 · Q3c(i)[1]
On Fig. 3.1, sketch the variation with F of the resistance R of the wire. R R 0 0 0 F
See it on the paper → - 9702/23 · October/November 2025 · Q5b(i)[2]
The thermistor has resistance R 0 at a temperature of 0 °C. On Fig. 5.2, sketch a possible variation of the resistance of the thermistor with temperature between 0 °C and 100 °C. R 0 0 0 temperature / °C 100 resistance
See it on the paper → - 9702/23 · October/November 2025 · Q5b(ii)[3]
With reference to the current in the cell, explain why the current in resistor R decreases with increasing temperature of the thermistor.
See it on the paper → - 9702/21 · May/June 2025 · Q6a(iii)[3]
Calculate the resistivity of the nichrome. resistivity = Ω m
See it on the paper → - 9702/23 · May/June 2025 · Q7a[3]
Calculate, to three significant figures, the resistance of the wire. resistance = Ω
See it on the paper → - 9702/51 · May/June 2025 · Q2b[1]
and I are given in Table 2.1. n Table 2.1 I / μA 5 0.200 455 ± 5 6 0.167 525 ± 5 7 0.143 580 ± 5 8 0.125 635 ± 5 9 0.111 685 ± 5 11 0.0909 765 ± 5 Calculate and record values of 1 / 10 3 A –1 I 1 n 1 1 / 10 3 A –1 in Table 2.1. Include the absolute uncertainties in . n (b) Values of n,
See it on the paper → - 9702/51 · May/June 2025 · Q2c(i)[2]
Plot a graph of 1 1 1 / 10 3 A –1 against . Include error bars for . I n I
See it on the paper → - 9702/51 · May/June 2025 · Q2c(ii)[2]
Draw the straight line of best fit and a worst acceptable straight line on your graph. Label both lines.
See it on the paper → - 9702/51 · May/June 2025 · Q2c(iii)[2]
Determine the gradient of the line of best fit. Include the absolute uncertainty in your answer. gradient = 2.3 2.2 2.0 1 / 10 3 A –1 I 1.9 1.8 2.1 1.7 1.6 1.5 1.4 1.3 1.2 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22 1 n
See it on the paper → - 9702/51 · May/June 2025 · Q2c(iv)[2]
Determine the y-intercept of the line of best fit. Include the absolute uncertainty in your answer. y-intercept =
See it on the paper → - 9702/51 · May/June 2025 · Q2d(i)[1]
R = Using your answers to (a), (c)(iii) and (c)(iv), determine the values of R and Z. Include appropriate units. (i)
See it on the paper → - 9702/51 · May/June 2025 · Q2d(ii)[1]
Determine the percentage uncertainty in your value of R. percentage uncertainty = %
See it on the paper → - 9702/51 · May/June 2025 · Q2e[1]
The experiment is repeated with 20 resistors, each of resistance R, connected in parallel between P and Q. Determine the total current I in the circuit. I = A
See it on the paper → - 9702/22 · February/March 2025 · Q6b(i)[2]
Show that the cross-sectional area of the wire is 1.3 × 10 –6 m 2 .
See it on the paper → - 9702/22 · February/March 2025 · Q6b(ii)[1]
Show that the number density of charge carriers in the wire is 8.3 × 10 28 m –3 .
See it on the paper → - 9702/22 · February/March 2025 · Q6c(i)[4]
State and explain how the resistance of wire Q compares with the resistance of wire P.
See it on the paper →
What examiners said
The majority of candidates gave the expression for the area in terms of the resistivity. The most common errors were with the powers of ten or rearranging the equation but generally this was well answered.
— Examiner report, February/March 2025, 9702/22 Q6(b)(i) (Cambridge)
This was generally well answered. The weaker candidates seemed to be unaware of the meaning of the number density of charge carriers. Some candidates attempted to use v = I/nAq but could not make progress as v is not known. Some candidates used this equation with their answer to 6(b)(iii) but this was not credited, as a ‘circular calculation’ is not valid in a ‘show that’ question.
— Examiner report, February/March 2025, 9702/22 Q6(b)(ii) (Cambridge)
This part of the question was challenging. Many candidates focussed on how the resistance of wire Q changes with its length instead of comparing the total resistance of wire Q with the total resistance of wire P. For example, there were many comments about the resistance of wire Q at the end of radius r1 or at the end of radius r2 and how those values compared to one another or to the resistance o...
— Examiner report, February/March 2025, 9702/22 Q6(c)(i) (Cambridge)
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