What is covered in OCR Gateway Physics A topics P7 Energy and P8 Global challenges?

P7 Energy covers energy stores and transfers, the conservation of energy and dissipation, work done, kinetic and gravitational potential energy, power and efficiency. P8 Global challenges covers physics on the move (stopping distances, momentum and vehicle safety), powering Earth (the national grid, transformers, mains electricity and energy resources) and beyond Earth (the Solar System, the life cycle of stars, red-shift and the Big Bang).

Which equations do I need for OCR P7 and P8?

Recall equations include work done equals force times distance, kinetic energy equals a half times mass times speed squared, gravitational potential energy equals mass times gravitational field strength times height, power equals energy transferred divided by time, and the electrical equations power equals potential difference times current, power equals current squared times resistance, and momentum equals mass times velocity. Given equations include efficiency (useful output over total input), the transformer power relationship, and stopping distance equals thinking distance plus braking distance.

Why is electricity transmitted at high voltage across the national grid?

For a given power, power equals potential difference times current, so a higher voltage means a lower current. The power wasted heating the transmission cables is proportional to the current squared, so a smaller current wastes far less energy as heat. Transmitting at high voltage and low current therefore makes the grid much more efficient over long distances, and step-down transformers then lower the voltage again for safe use.

How are OCR P7 and P8 examined?

P7 and P8 sit on the Paper 2 or Paper 4 side, which is synoptic and assumes the earlier topics. Expect multiple choice and structured questions: work, energy and power calculations, efficiency calculations, evaluating energy resources (often a six-mark question), national grid and transformer questions, stopping-distance and vehicle-safety questions, and descriptions of star life cycles and red-shift evidence for the Big Bang.

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OCR Gateway GCSE Physics A topics P7 Energy and P8 Global challenges overview

An overview of topics P7 Energy and P8 Global challenges in OCR Gateway GCSE Physics A (J249), mapping energy stores and transfers, work, energy and power, efficiency and energy resources, the national grid and mains electricity, vehicle safety and stopping distances, and the Solar System and the universe, with the recall and given equations and how the topics are examined.

Generated by Claude Opus 4.88 min readOCR J249 P7 and P8Updated 2026-06-02

Reviewed by: AI editorial process; not yet individually human-reviewed

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The P7 Energy content
The P8 Global challenges content
How P7 and P8 are examined
How to study P7 and P8
For the official specification

Topics P7 Energy and P8 Global challenges of OCR Gateway GCSE Physics A (specification J249) bring together energy ideas and apply physics to real-world challenges: efficient energy use, transport safety, the electricity supply and the wider universe. They are examined on the Paper 2 or Paper 4 side. This page maps both topics and links to a focused answer page for each part.

The P7 Energy content

Energy stores and transfers (P7.1): The energy stores, the four transfer pathways, the conservation of energy, and dissipation to the surroundings. See Energy stores and transfers.
Work, energy and power (P7.1): Work done as energy transferred by a force, the work done equation, the kinetic and gravitational potential energy equations, and power. See Work, energy and power.
Efficiency and energy resources (P7.2 and P8.2): Efficiency and the efficiency equation, reducing wasted energy, and comparing renewable and non-renewable resources. See Efficiency and energy resources.

The P8 Global challenges content

The national grid and mains electricity (P8.2 Powering Earth): Step-up and step-down transformers, high-voltage low-current transmission, the transformer power relationship, and mains electricity. See The national grid and mains electricity.
Vehicle safety and stopping distances (P8.1 Physics on the move): Thinking and braking distances and their factors, the energy and force in braking, momentum, and how safety features reduce injury. See Vehicle safety and stopping distances.
The Solar System and the universe (P8.3 Beyond Earth): The Solar System, the life cycle of stars, red-shift, and the evidence for the Big Bang. See The Solar System and the universe.

How P7 and P8 are examined

Both topics are assessed on the Paper 2 or Paper 4 side, each paper being 1 hour 45 minutes, worth 90 marks and 50% of the GCSE. Because this side is synoptic, it assumes the P1 to P6 content. Section A is multiple choice; Section B is short answer, structured, maths and practical questions, including a six-mark level of response question (often the evaluation of energy resources). Expect work, energy, power and efficiency calculations, national grid and transformer questions, stopping-distance and vehicle-safety questions, and star and red-shift questions.

How to study P7 and P8

Drill the recall equations. Work done, kinetic energy, gravitational potential energy, power and momentum must be automatic; remember kinetic energy goes as the speed squared.
Use the given equations correctly. Efficiency (useful over total), the transformer power relationship, and stopping distance as thinking plus braking come from the data sheet.
Reason about the grid. High voltage gives low current, and the heating loss goes as the current squared, so low current is efficient.
Split stopping distance. Reaction-time factors change the thinking distance; road and car conditions change the braking distance.
Learn the star route by mass. A Sun-sized star ends as a white dwarf; a much heavier star ends as a supernova then a neutron star or black hole. Red-shift is the evidence for the expanding universe and the Big Bang.

For the official specification

OCR publishes the full specification, past papers and mark schemes at ocr.org.uk. Always revise from the current specification and OCR's own past papers, because question style and the equation sheet are board-specific.

Sources & how we know this

OCR GCSE (9-1) Physics A (Gateway Science) J249 specification — OCR (2016)