plumiE.m.f., internal resistance and power: OCR A‑Level Physics B questions
OCR A-Level Physics B past-paper questions on 3.1.2.3 E.m.f., internal resistance and power, 2016–2025, with mark schemes and examiner’s reports where available.
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All 59 questions on E.m.f., internal resistance and power, as a list
- June 2025, Paper 1, Q5 (1 mark): Two identical cells are connected in series. The e.m.f. of each cell is ε and the internal resistance of each cell is r. Which row shows the combined e.m.f. and
- June 2025, Paper 1, Q6 (1 mark): A number of identical resistors are connected in parallel to a cell of negligible internal resistance. Which graph shows how the power dissipated in the circuit
- June 2025, Paper 2, Q4(a)(i) (2 marks): Explain the difference in the meaning of the terms e.m.f. and potential difference. [2]
- June 2025, AS Paper 1, Q18 (1 mark): 1.0 Ω 1.6 A 6.0 Ω In the circuit shown above, what is the value of the cell e.m.f.? A 1.6 V B 8.0 V C 9.6 V D 11.2 V Your answer [1]
- June 2025, AS Paper 2, Q1(a) (4 marks): The student concludes that the e.m.f. of the cell is 1.5 V and that its internal resistance is 1.2 Ω. Explain how the student reaches these conclusions. Include
- June 2025, AS Paper 2, Q5(b)(ii) (4 marks): The density of a substance is given by the equation density (ρ) = mass (m) ÷ volume (V). The density of nichrome is 8400 kg m–3. The specific thermal capacity o
- June 2025, AS Paper 2, Q5(b)(iii) (4 marks): A resistor of the same value can be made using a thicker wire of the same nichrome alloy. Explain the advantages and disadvantages of using thicker wire to make
- June 2024, Paper 1, Q21 (1 mark): The graph shows how a quantity y changes when a quantity x changes. y 0 x 0 Which row of the table shows two examples of quantities x and y that have the relati
- June 2024, Paper 1, Q26 (1 mark): The diagram shows identical resistors connected in parallel to a cell with negligible internal resistance. Which graph shows how the power P, dissipated in the
- June 2024, AS Paper 1, Q26(a) (3 marks): Identify the independent variable, the dependent variable and the most significant variable that must be controlled in this experiment. Tick one box in each col
- June 2024, AS Paper 1, Q26(b) (1 mark): The teacher’s measurements are shown in the table below. Internal Length / cm Terminal p.d. / V Current / mA Resistance / Ω 30 8.64 297 1.212 45 8.68 266 60 8.7
- June 2023, Paper 1, Q22 (1 mark): A d.c. power supply is connected to a resistor combination as shown. The ammeter reads 2.0 A. The p.d. across the 3.0 Ω resistor is 6.0 V. d.c. supply 3.0 Ω A 1
- June 2023, Paper 3, Q1(a)(iii) (3 marks): Find the gradient of the line of best fit and hence calculate the lemon’s internal resistance, in ohms, Ω. Show your working. Internal resistance = Ω [3]
- June 2023, Paper 3, Q1(a)(iv) (2 marks): A student suggests that two lemon cells in series could be used to run a 1.5 V, 0.45 W filament lamp. Explain why this is not correct. [2]
- June 2023, Paper 3, Q1(b) (6 marks): A cell can be made by inserting a zinc cathode and a copper anode into a lemon. A high resistance voltmeter is used in the circuit shown in Fig. 1.1 to measure
- June 2023, AS Paper 1, Q3 (1 mark): The emf of the cell is: A 1.6 V B 10.4 V C 12.0 V D 13.6 V Your answer [1]
- June 2023, AS Paper 1, Q4 (1 mark): The power dissipated in the internal resistance is: A 2.56 J B 2.56 W C 19.2 J D 19.2 W Your answer [1]
- June 2022, Paper 1, Q8 (1 mark): The emf of the cell in the circuit shown is 2.7 V. The high resistance voltmeter reads 2.4 V. 2.7 V r 0.8 Ω V What is the internal resistance r of the cell? A 0
- June 2022, Paper 1, Q9 (1 mark): What is the power transferred in the cell in the circuit shown? A 0.1 W B 0.9 W C 8.1 W D 9.1 W Your answer [1]
- June 2022, AS Paper 1, Q19 (1 mark): The diagram shows a circuit with a battery that has internal resistance r and EMF of 12.0 V. 12.0 V r 1.6 A 6.0 Ω The value of the internal resistance r is: A 1
- June 2022, AS Paper 2, Q3(b) (2 marks): Without calculation, state and explain how the voltmeter reading would differ from the answer to (a) if the battery internal resistance were not negligible. [2]
- November 2021, Paper 1, Q1 (1 mark): Which expression gives a quantity that can be expressed in watts? A F s where F is the force causing a body to move and s is its displacement I 2 R B where I is
- November 2021, Paper 1, Q13 (1 mark): Kirchhoff’s Second Law states that the sum of the potential differences around any closed loop in the circuit must be zero. E r R1 I1 R3 I3 R2 I2 Here are three
- November 2021, Paper 1, Q36(a) (6 marks): This question considers the internal resistance of chemical cells. (a)* Explain how you would practically measure the internal resistance of a 1.5 V cell. Inclu
- November 2021, Paper 1, Q36(b)(ii) (2 marks): The graph shows the potential difference of the cell against time as it completely discharges at a constant load current of 4.5 A. 5 p.d. / V 4 3 0.3 r / Ω 2 0.
- November 2021, AS Paper 1, Q10 (1 mark): Which graph shows the relationship between electrical power P and current I through an ohmic resistor? A B C D P P P P I I I I Your answer [1]
- November 2021, AS Paper 1, Q27(a) (2 marks): Explain what is meant by the term e.m.f. [2]
- November 2021, AS Paper 1, Q27(b) (3 marks): Calculate the internal resistance of the cell. resistance = Ω [3] 21 A student records the p.d. and current values for several different values of the variable
- November 2021, AS Paper 1, Q27(d)(i) (1 mark): The e.m.f. of the cell. e.m.f. = V [1]
- November 2021, AS Paper 1, Q27(d)(ii) (2 marks): The internal resistance. resistance = Ω [2]
- November 2021, AS Paper 2, Q4 (3 marks): A 230 V electric kettle has a power of 2.0 kW and a resistance of 26 Ω. The heating element contains coiled nichrome wire of total length 4.8 m. The electrical
- November 2021, AS Paper 2, Q7(a) (4 marks): Modern electric cars use rechargeable batteries. The older fork-lift trucks, used on the flat floors of warehouses, also use rechargeable batteries. In each cas
- November 2021, AS Paper 2, Q7(b)(i) (1 mark): Use data from Table 7.1 to show that the total energy stored in the fully-charged lithium- ion battery is about 250 MJ. [1] Table 7.2 contains data for a typica
- November 2021, AS Paper 2, Q7(b)(ii) (2 marks): At the maximum power, the motor draws a current of 230 A. Calculate the resistance of the motor under these conditions. You can assume that the internal resista
- November 2021, AS Paper 2, Q7(b)(iii) (2 marks): Assuming that travelling for the given range at a speed of 80 km h–1 discharges the battery completely, show that the mean power drawn from the battery is about
- November 2021, AS Paper 2, Q7(c) (6 marks): This question is about electric vehicles (EVs). heavy load electric car being charged fork-lift truck in use Fig. 7.1 (c)* Table 7.3 displays data for two diffe
- November 2020, Paper 3, Q1(b)(ii) (4 marks): The following readings were obtained: potential difference V = 10.5 ± 0.2 V current I = 2.3 ± 0.2 A. Calculate the power supplied to the heater per unit mass of
- November 2020, AS Paper 1, Q9 (1 mark): A high resistance voltmeter, connected to the terminals of a cell, reads 1.5 V. When an 8.0 Ω resistor is connected in parallel with the voltmeter, the p.d. dro
- November 2020, AS Paper 1, Q23(a) (3 marks): Calculate the power dissipated in the heater when the current is 2.4 A and give the unit. power dissipated = unit [3] The student replaces the heater with a dif
- November 2020, AS Paper 1, Q23(b) (3 marks): Calculate the amount of energy transferred by the heater. energy = J [3] The student finds information in a text book that suggests this amount of energy should
- June 2019, Paper 1, Q9 (1 mark): The circuit shows a potential divider with resistors of R and 4R. V R 4R power dissipated in resistor R What is the ratio power dissipated in resistor 4R? 1 A 1
- June 2019, Paper 1, Q40(a)(i) (1 mark): Use the initial gradient of the graph to calculate the internal resistance of the cell under this illumination. internal resistance = Ω [1]
- June 2019, Paper 1, Q40(b) (6 marks): Fig. 40.1 shows the voltage–current characteristic for an illuminated solar cell. 3.5 p.d. / V 3.0 2.5 2.0 1.5 1.0 0.5 0 0 10 20 30 40 50 60 70 80 I / mA Fig. 4
- June 2019, Paper 2, Q2(c)(ii) (3 marks): When a digital voltmeter of resistance 1.0 MΩ replaces the analogue voltmeter in Fig. 2.2, it registers a potential difference of 0.93 V. Use the readings from
- June 2018, Paper 1, Q1 (1 mark): Which expression gives a quantity that can be expressed in joules? A F v where F is the force causing a body to move and v is its speed I 2 R B where I is the c
- June 2018, Paper 1, Q7 (1 mark): These two circuits use identical components. The cells have zero internal resistance. V V R R R R circuit 1 circuit 2 What is the ratio power dissipated in circ
- June 2018, Paper 1, Q34(a) (2 marks): Show that the initial current charging the rechargeable battery I is less than 0.2 A. [2]
- June 2018, AS Paper 1, Q9 (1 mark): There is a current of 5.0 mA in a 250 Ω resistor for 40 minutes. How much energy is dissipated in the resistor? 2.5 × 10−6 J A B 1.5 × 10−4 J C 0.25 J D 15 J Yo
- June 2018, AS Paper 2, Q6(a) (6 marks): Fig. 6.1 represents a cell of e.m.f. f and internal resistance r. A and B are the positive and negative terminals of the cell. f r A B + – Fig. 6.1 (a)* Complet
- June 2018, AS Paper 2, Q6(b)(ii) (3 marks): Calculate the time taken for the discharge. time = s [3]
- June 2018, AS Paper 2, Q6(b)(iii) (3 marks): Show that the percentage efficiency of energy transfer to the load resistance R is given by R percentage efficiency = 100 × R + 2r where r is the internal resis
- June 2018, AS Paper 2, Q6(c) (3 marks): Lithium-ion rechargeable batteries are used for a large number of charge-discharge cycles. Fig. 6.2 shows how the energy stored in such a battery changes with t
- June 2017, Paper 1, Q33(a)(ii) (2 marks): Calculate the time it will take the heater to deliver this amount of thermal energy. time = s [2]
- June 2017, AS Paper 1, Q12 (1 mark): Which is an expression for energy? A Fv where F is the force causing a body to move and v is its speed. I2R where I is the current in a resistance of value R. B
- June 2017, AS Paper 1, Q20 (1 mark): The resistors below are identical. Each combination is connected in a circuit to a 6 V battery of negligible internal resistance. For which combination is the m
- June 2017, AS Paper 1, Q21(d) (2 marks): Calculate the power supplied by the battery. power = W [2]
- June 2016, AS Paper 1, Q17 (1 mark): A digital voltmeter of very high resistance is connected across the terminals of a source of e.m.f. The voltmeter reads 12 V. When an analogue voltmeter with a
- June 2016, AS Paper 1, Q20 (1 mark): In the diagram below, the battery of e.m.f 6 V has negligible internal resistance. 6 V 10 Ω 5 Ω What is the power dissipated in the 10 Ω resistor in the circuit
- June 2016, AS Paper 2, Q4(d) (4 marks): Compact fluorescent lamps (CFLs) are energy efficient but they contain toxic mercury. White light LEDs are now rapidly replacing CFLs in many applications. The
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