A maglev train uses the motor effect to accelerate along a track. Explain how increasing the current in the train's electromagnets and reversing the direction of the current each affect the force experienced by the train.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Maglev trains use powerful electromagnets carrying large currents placed within magnetic fields to produce the forces needed for acceleration and braking.
Model answer (4 marks)
Increasing the current increases the magnetic field strength around the electromagnet, which, according to the motor effect, increases the force on the train.
Reversing the direction of the current reverses the direction of the magnetic field relative to the track, so the force on the train is reversed.
Fleming’s left‑hand rule shows that the force direction depends on the relative directions of current and field, so changing the current direction changes the force direction.
Thus, higher current gives a larger forward force, while reversing current changes the force direction, allowing acceleration or braking.
Reversing the direction of the current reverses the direction of the magnetic field relative to the track, so the force on the train is reversed.
Fleming’s left‑hand rule shows that the force direction depends on the relative directions of current and field, so changing the current direction changes the force direction.
Thus, higher current gives a larger forward force, while reversing current changes the force direction, allowing acceleration or braking.
Examiner tips
- Use the motor effect formula F=ILB to link current and force.
- Show the effect of current direction with Fleming’s left‑hand rule.
- Keep the answer concise and use the exact terminology.
- Explain both magnitude and direction changes.
Mark scheme (4 marks)
- Increasing the current increases the strength of the magnetic field around the wire / electromagnet
- A stronger magnetic field results in a greater force on the train (motor effect)
- Reversing the direction of the current reverses the direction of the force on the train
- This can be determined / explained using Fleming's left-hand rule, where the direction of the force depends on the direction of the current relative to the magnetic field
Key terms in this question
motor effect · current · force
Related
- All AQA GCSE Physics (8463) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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