OCR Gateway GCSE Physics A topic P4 Magnetism and magnetic fields overview

Topic P4 Magnetism and magnetic fields of OCR Gateway GCSE Physics A (specification J249) is about magnets, the magnetic effect of a current, and how changing fields induce voltages in generators and transformers. It is examined on the Paper 1 or Paper 3 side. This page maps the topic and links to a focused answer page for each part.

The P4 Magnetism content

Magnets and magnetic fields (P4.1)

Permanent and induced magnets, magnetic materials, attraction and repulsion, the field around a bar magnet and the Earth, and the plotting compass. See Magnets and magnetic fields.

Electromagnets and the motor effect (P4.2)

The field around a wire and a solenoid, electromagnets and their strength, the motor effect, Fleming's left-hand rule, and the electric motor. See Electromagnets and the motor effect.

Induction, generators and transformers (P4.2)

Electromagnetic induction, the factors affecting the induced voltage, the generator, and step-up and step-down transformers. See Electromagnetic induction, generators and transformers.

How P4 is examined

P4 is assessed on the Paper 1 or Paper 3 side, each paper being 1 hour 45 minutes, worth 90 marks and 50% of the GCSE. Section A is multiple choice; Section B is short answer, structured, maths and practical questions, including a six-mark level of response question. Much of P4 is descriptive: drawing and interpreting magnetic fields, applying Fleming's left-hand rule, and explaining motors, generators and transformers. The grid link to $P = VI$ and $P = I^2 R$ is a common synoptic theme.

How to study P4 Magnetism

1. Master magnetic fields. Know the bar-magnet field, the wire's circular field, and the solenoid's bar-magnet-like field.
2. Use repulsion as the magnet test. Only a permanent magnet repels; magnetic materials are only attracted.
3. Learn Fleming's left-hand rule. First finger field, second finger current, thumb force, using the left hand.
4. Know what strengthens an electromagnet. More current, more turns, or an iron core.
5. Explain induction and transformers. The field must be changing to induce a voltage; transformers need a.c. and underpin the national grid.

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.