OCR GCSE Physics A: Energy resources, trends in use and mains electricity (J249) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover OCR GCSE (9-1) Physics A (Gateway Science), J249, Version 5.0 (July 2026), statements P8.2a, P8.2b and P8.2g to P8.2j. All of them are suitable for both tiers. Read the study guide first if a topic is new, and use the revision notes to check facts. The course hub is OCR GCSE Physics and the printable list is the checklist.

Questions

1. The list shows six energy resources: coal, tides, uranium, biofuel, natural gas, hydroelectricity. State the three that are renewable. [3]

2. Explain why uranium is classed as a non-renewable energy resource. [2]

3. Describe how the energy of water stored behind a dam is used to generate electricity, and state one advantage of this over a coal-fired power station. [4]

4. The table shows the electricity generated, in TWh, from five sources in a country in two years.

Source	2000	2024
Oil	40	12
Coal	95	30
Gas	110	130
Wind	6	70
Solar	0	28

(a) Calculate the percentage change in the electricity generated from gas between 2000 and 2024. [2] (b) Calculate the share of the total that came from wind in 2000 and in 2024. Give each answer as a percentage to 1 decimal place. [2] (c) Suggest one reason for the fall in the use of coal. [1]

5. Compare solar energy and tidal energy as resources for generating electricity. [4]

6. A farm grows crops to make biofuel. (a) Explain why biofuel is a renewable resource. [2] (b) State one disadvantage of growing crops for biofuel. [1]

7. (a) State the difference between a direct potential difference and an alternating potential difference. [2] (b) Give one source of each. [1]

8. A data logger records the UK mains supply. The time base is 2.5 ms per division. One complete wave on the trace takes up 8 divisions. (a) Calculate the period of the wave. [2] (b) Calculate the frequency of the wave. [2] (c) Calculate the number of complete cycles in one minute. [1]

9. (a) State the function of each of the live, neutral and earth wires in a mains cable. [3] (b) State the approximate potential difference between the live wire and the neutral wire in the UK. [1]

10. A toaster is wired so that its switch is in the neutral wire instead of the live wire. Explain why the toaster may still be dangerous when the switch is open. [4]

11. A kettle has a metal case. Its live wire becomes loose inside and touches the case. (a) Explain the danger if the case is not connected to the earth wire. [2] (b) Explain how a connection between the case and the earth wire changes the situation. [2] (c) State the purpose of the insulation around the wires. [1]

12. A coal-fired power station has an output of 900 MW. A wind farm has an average output of 9 MW. (a) Calculate the energy transferred by the power station in 6 hours, in megawatt-hours. [2] (b) Calculate how many wind farms of this average output would be needed to match the power station. [2] (c) Explain two reasons why a country could not simply replace the power station with wind farms alone. [2] (d) State the frequency of the mains supply in the UK, and calculate the number of cycles in 0.5 s. [2]

Answers

1. Tides [1], biofuel [1], hydroelectricity [1]. [3] Examiner insight: Name exactly three. Adding extra resources to the list risks including a wrong one.

2. It is used faster than it forms [1], so the supply is limited and will run out [1]. [2] Examiner insight: “It runs out” alone is thin. Say why: it takes far longer to form than the rate at which we use it.

3. Water stored at a height flows downhill [1]. It passes through turbines and turns them [1]. The turbines turn generators that produce electricity [1]. Advantage: no carbon dioxide is released when generating, or output can be adjusted quickly [1]. [4] Examiner insight: A describe question rewards the chain of events in order. State the advantage as a comparison with coal, not just a feature.

4. (a) Change = 130 − 110 = 20 TWh [1]. Percentage change = 20 ÷ 110 × 100 = 18.2% increase [1]. (b) Totals: 2000 is 251 TWh and 2024 is 270 TWh. Share in 2000 = 6 ÷ 251 × 100 = 2.4% [1]. Share in 2024 = 70 ÷ 270 × 100 = 25.9% [1]. (c) Coal is a non-renewable fossil fuel that releases carbon dioxide when burned, so it has been replaced by renewable sources such as wind and solar [1]. [5] Examiner insight: Divide by the starting value for percentage change and by the total for a share. Show the total used so your method is visible.

5. Both are renewable and need no fuel [1]. Solar output depends on daylight and cloud, so it varies [1]. Tidal output varies but is predictable because tides can be forecast [1]. Tidal schemes need suitable coastal sites, while solar panels can be fitted in many places [1]. [4] Examiner insight: A compare question needs both resources in each point. Listing facts about one resource and then the other with no link gains less.

6. (a) The crops can be regrown [1], so the fuel is replaced about as fast as it is used [1]. (b) Land is used for fuel instead of for food, or growing takes time and land [1]. [3] Examiner insight: Link the reason for “renewable” to replacement. “It is natural” is not enough.

7. (a) In a direct p.d. the direction stays the same [1]. In an alternating p.d. the direction reverses repeatedly [1]. (b) Direct: a cell or battery. Alternating: the mains supply [1]. [3] Examiner insight: Give both parts of the contrast. Describing only a.c. leaves the d.c. half unstated.

8. (a) Period = 8 × 2.5 ms [1] = 20 ms (0.020 s) [1]. (b) Frequency = 1 ÷ 0.020 [1] = 50 Hz [1]. (c) 50 × 60 = 3000 cycles [1]. [5] Examiner insight: Convert milliseconds to seconds before using f = 1 ÷ T, and include the unit with each answer.

9. (a) Live: carries the alternating p.d. from the supply to the appliance [1]. Neutral: completes the circuit [1]. Earth: a safety wire connected to the metal case that carries no current in normal use [1]. (b) About 230 V [1]. [4] Examiner insight: Give a function for each wire. Describing the earth wire as “the wire that carries current back” confuses it with the neutral.

10. The switch only breaks the neutral wire [1]. The appliance remains connected to the live wire at about 230 V [1]. A person who touches a conducting part provides a path to earth [1]. A current passes through the person, causing a shock [1]. [4] Examiner insight: Say that the live wire is still connected. Saying only that the toaster “is still on” does not explain the danger.

11. (a) The metal case becomes live at about 230 V [1]. A person who touches it provides a path to earth and gets a shock [1]. (b) The case is at 0 V through the earth wire, with a large p.d. across the loose live wire [1]. A large current flows through the earth wire instead of through the user [1]. (c) To stop a person touching the live conductor and to stop contact with other conductors [1]. [5] Examiner insight: For an explain question, connect each effect to the one before it: touching the case, large p.d., current through the body.

12. (a) Energy = power × time = 900 MW × 6 h [1] = 5400 MWh [1]. (This is 1.9 × 10^13 J to 2 significant figures.) (b) 900 ÷ 9 [1] = 100 wind farms [1]. (c) Wind output depends on the weather, so it cannot be relied on [1]. Fossil stations can run whenever demand needs them, but wind farms cannot [1]. (Other valid reasons: land and set-up, effect on the landscape.) (d) 50 Hz [1]. Cycles in 0.5 s = 50 × 0.5 = 25 cycles [1]. [8] Examiner insight: In an extended question every part still needs its own working. A correct power-times-time answer needs the unit.

Where marks are usually lost

• Calling a resource renewable because it is cheap or clean, instead of because it is replaced.
• Dividing by the wrong number: the starting value for percentage change, the total for a share.
• Leaving off units such as TWh, MWh, Hz and ms, or leaving off the percentage sign.
• Using the time base in milliseconds without converting before f = 1 ÷ T.
• Mixing up the functions of the neutral wire and the earth wire.
• Writing “current” where “potential difference” is meant when describing the live wire at 230 V.
• Saying a switch in the neutral wire is safe because the appliance stops working.
• Giving a feature of one resource and not comparing it with the other in a compare question.
• Writing “trend” answers without figures from the data.

Next steps

• Review the revision notes and the study guide.
• Go to the OCR GCSE Physics hub and tick off topics on the checklist.
• Try the free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

OCR GCSE (9-1) Physics A (Gateway Science) specification (J249), Version 5.0 (July 2026), for first assessment in 2018, published by OCR.