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Detailed notes on Electromagnetic Effects for Cambridge IGCSE Coordinated Science, covering key concepts, explanations, examples, and exam-focused revision points.
A changing magnetic field induces an e.m.f. in a conductor. Cambridge tests Faraday's and Lenz's laws, how to increase induced e.m.f., and the use of Fleming's right-hand rule for generators.
Mapped to the Cambridge IGCSE 0654 syllabus (2025-2027).
Moving a magnet relative to a coil induces e.m.f. — the basis of all generators.
Electromagnetic induction:
Ways to induce an e.m.f.:
Faraday's Law:
The magnitude of the induced e.m.f. is proportional to the rate of change of magnetic flux.
Lenz's Law:
The direction of the induced current is such that it opposes the change that caused it.
Factors that increase the induced e.m.f.:
Fleming's Right-Hand Rule (generator effect):
Demonstrating induction:
Verbatim phrases and definitions Cambridge mark schemes credit.
Paper 4: 'A magnet is pushed into a coil connected to a galvanometer. State what is observed and explain why' (3 marks — galvanometer deflects; changing flux through coil induces e.m.f.; current flows in completed circuit). 'State what happens to the deflection if the magnet is pulled out at the same speed' (1 mark — deflects in opposite direction). 'State TWO ways to increase the size of the induced e.m.f.' (2 marks — move magnet faster / use stronger magnet / more turns). 'State Lenz's law' (2 marks).
Sources: Cambridge IGCSE Coordinated Sciences 0654 syllabus 2025-2027 (P7); 0654 Examiner Reports 2022-2024. Last reviewed 2026-05-14.
Step-by-step solutions to past-paper-style questions on electromagnetic induction , written exactly the way a tutor would explain them at the board.
Question
A bar magnet is pushed toward a coil connected to a galvanometer. The galvanometer deflects. Explain why and state what happens to the deflection when (a) the magnet moves faster and (b) the magnet is held stationary.
Step-by-step solution
Step 1
Moving the magnet toward the coil increases the magnetic flux through the coil. This changing flux induces an EMF in the coil (Faraday's law), which drives a current detected by the galvanometer.
Step 2
(a) Faster movement → faster rate of change of flux → larger induced EMF → larger galvanometer deflection.
Step 3
(b) Stationary magnet → no change in flux → no induced EMF → no deflection. (Zero reading on galvanometer.)
Answer
Moving magnet changes flux → induced EMF → current. (a) Faster → larger EMF/deflection. (b) Stationary → no EMF, zero deflection.
Question
A magnet's north pole is moved toward the left face of a coil. Determine the polarity of the left face of the coil and explain using Lenz's law.
Step-by-step solution
Step 1
Lenz's law: the induced current opposes the change that caused it. The north pole approaching increases the flux through the coil.
Step 2
To oppose the increase, the induced current must create a magnetic field opposing the magnet's field at the left face. The left face must become a north pole (like poles repel the approaching magnet, opposing its motion).
Step 3
Using the right-hand grip rule (or corkscrew rule): the current in the coil flows anticlockwise when viewed from the left (to produce a north pole on the left face).
Answer
Left face becomes a north pole (repelling the approaching north pole). Current flows anticlockwise viewed from the left — consistent with Lenz's law.
Question
A coil with 200 turns and cross-sectional area 50cm2 is in a magnetic field. The field changes from 0.10T to 0.40T in 0.50s. Estimate the induced EMF.
Step-by-step solution
Step 1
Change in flux through one turn.
ΔΦ=ΔB×A=(0.40−0.10)×50×10−4=0.30×5.0×10−3=1.5×10−3Wb
Step 2
Induced EMF (Faraday's law): ε=NΔtΔΦ.
ε=200×0.501.5×10−3=200×3.0×10−3=0.60V
Answer
Induced EMF ≈0.60V
Examiner tip
At Extended IGCSE, the full Faraday calculation is occasionally assessed. Check whether the syllabus requires the numerical form or just qualitative understanding.
The formulae you need to memorise for electromagnetic induction on the Cambridge IGCSE 0654 paper, with every variable defined in plain English and a note on when to use it.
ε=NΔtΔΦ
When to use
Calculating the induced EMF when the rate of flux change and number of turns are known.
Definitions to memorise and the exact keywords mark schemes credit for electromagnetic induction answers — sharpened from recent examiner reports for the 2026 0654 sitting.
The induced EMF in a conductor is directly proportional to the rate of change of magnetic flux through the conductor.
The direction of an induced current is always such that it opposes the change in flux that caused it (conservation of energy).
The energy transferred per unit charge by a source (such as a generator or cell). SI unit: volt (V). Not to be confused with potential difference (which is the energy transferred per unit charge by an external circuit element).
The product of the magnetic flux density and the area of the conductor perpendicular to the field. Φ=BAcosθ; SI unit: weber (Wb). A changing flux induces an EMF.
The traps other students keep falling into on electromagnetic induction questions — taken from recent Cambridge IGCSE 0654 examiner reports and mark schemes — and how to avoid them.
Why it happens
Students think the presence of a magnetic field is enough to induce current.
How to avoid it
Induction requires CHANGING flux. A stationary magnet produces a constant flux → no induction. Flux must be changing (magnet moving, or field strength changing).
Why it happens
Students remember 'opposing' but apply it to the wrong quantity.
How to avoid it
The induced current opposes the change in flux that caused it (not the flux itself). North pole approaching → coil becomes a north pole to repel → opposing motion.
Why it happens
Students say 'moving the magnet causes induction' without specifying rate.
How to avoid it
The key is the RATE of change of flux. Faster movement = greater rate of change = larger induced EMF.
The things students keep getting wrong in this sub-topic, answered.