Electromagnetic Induction

🎯 Exam Focus

Frequently Examined

Electromagnetic induction is examined across several question types. Examined in Edexcel 1PH0/2 (Paper 2). Edexcel uses context-based questions — wind turbines, generators in power stations, microphones, bicycle dynamos — so practise applying induction principles to unfamiliar scenarios.

• Conditions for induction (2 marks): Must state that the magnetic field must be CHANGING. A stationary magnet produces no voltage. Award both marks: state the condition AND what happens when it is not met.
• Increasing induced voltage (2-3 marks): Three factors — move faster, stronger magnet, more turns on coil. Each factor plus a reason earns a mark.
• Reversing current direction (2 marks): Either reverse the motion OR flip the magnet. Both are valid for full marks.
• AC generator vs DC dynamo (3 marks): Slip rings give AC output; split-ring commutator gives DC output. Explain why the output differs for each.
• Lenz's law / direction of induced current (2-3 marks): State that the induced current opposes the change that caused it, and name what is being opposed (the motion or the change in flux). Link to conservation of energy for the higher marks.
• Transformers and the National Grid (HT, 4-6 marks): Explain why high voltage transmission reduces power lost as heat (P = I²R), and why transformers only work with AC.
• "Suggest" questions (Edexcel): Given a novel generator or sensor design, suggest how its output voltage could be increased or its current direction reversed — apply the three induction factors.