IGCSE §6: Magnetism and Electromagnetism · IGCSE
Magnets and Magnetic Fields
Revision notes on Magnets and Magnetic Fields for the OCR A-level Physics specification (H556). Free to read, with 4 practice questions in the app.
Magnetic pole — a region of a magnet where the magnetic force is strongest. Every magnet has a north-seeking (N) pole and a south-seeking (S) pole, and poles always come in pairs. Cut a magnet in half and you get two shorter magnets, never a single isolated pole.
The law of magnets:
- Like poles repel — N and N, or S and S.
- Unlike poles attract — N and S.
Magnetic field — the region around a magnet in which a magnetic material or another magnet experiences a force.
Field lines are drawn to represent it, and they follow strict conventions:
- They run from north to south outside the magnet.
- The arrow shows the direction of the force on a north pole placed there.
- They are closest together where the field is strongest, which is at the poles.
- They never cross. Two crossing lines would mean the field pointed in two directions at one place, which is impossible.
Attraction and repulsion patterns. Between unlike poles the lines run straight across from one magnet to the other. Between like poles the lines curve away from each other, and there is a neutral point in the middle where the two fields cancel exactly and the resultant field is zero.
Plotting a field:
- Iron filings — sprinkle over paper laid on the magnet and tap gently. The filings line up along the field lines and show the shape at a glance, but give no direction.
- A plotting compass — place it at a point and mark where the needle points, then move it along and repeat. Slower, but it gives the direction as well as the shape.
The Earth behaves like a giant bar magnet, which is why a compass works. Note the awkward consequence: the needle's north-seeking pole points towards the geographic North Pole, so the Earth's magnetic pole up there is actually a magnetic south pole. Unlike poles attract, and the naming is historical.
Example: two bar magnets are laid end to end with their north poles facing. Iron filings show lines bulging away from the gap, and a compass placed exactly midway barely deflects at all — that is the neutral point.
4 questions on Magnets and Magnetic Fields
Reading is not revising. This topic has 4 questions in the app — multiple choice, calculations, and written answers marked against the mark scheme, point by point. Miss one and it comes back later with its options reshuffled, so you have to know it rather than remember where the answer sat.
- Every topic of Edexcel International GCSE Physics (4PH1)
- Flashcards and every equation, linked to the topic it comes from
- Full mock papers in the real paper structure
20 minutes a day is free. No card, nothing to cancel — and the paid version never renews itself either.
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