Magnetism & Electromagnetism is a core part of GCSE Physics. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Generator effectMoving a wire in a field induces a voltage
Right-hand ruleUsed for generators — same fingers, opposite hand
AlternatorAC generator — uses slip rings
DynamoDC generator — uses a split-ring commutator
TransformerTwo coils on an iron core that change voltage
Vp/Vs = Np/NsVoltage ratio equals turns ratio in a transformer
SolenoidCoil of wire — makes a uniform field like a bar magnet
ElectromagnetSolenoid with an iron core — magnetism you can switch
Motor effectA current in a magnetic field feels a force
F = B × I × LForce (N) = field (T) × current (A) × length (m)
Left-hand ruleThumb force, first finger field, second finger current
TeslaUnit of magnetic flux density, symbol T
Magnetic poleEnd of a magnet — north or south
Pole ruleLike poles repel, unlike poles attract
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
What happens to the current as it goes around a series circuit?✗ Current gets used up by each component as it flows around the circuit. ✓ It stays the same at every point — current is conserved.
What is the main difference between an alternator and a dynamo?✗ Alternator is for cars only ✓ Alternator uses slip rings (AC); dynamo uses a split-ring commutator (DC)
Which change does NOT increase the induced voltage in a coil?✗ Spinning the coil faster ✓ Using fewer turns of wire
What produces a magnetic field around a wire?✗ The metal in the wire is naturally magnetic. ✓ A moving electric charge — i.e. an electric current.
If an object is moving at constant velocity in a straight line, what is the net force on it?✗ There must be a forward force on the object to keep it moving. ✓ Zero — by Newton's first law, constant velocity requires zero net force.
Practise Magnetism & Electromagnetism — free games
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