A student wraps a length of wire into a solenoid and connects it to a battery. Explain how the student could increase the strength of the magnetic field produced by the solenoid, giving two different methods.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A solenoid is a wire wrapped into the shape of a coil. It produces a strong and relatively uniform magnetic field along its centre.
Model answer (4 marks)
Increase the current through the solenoid – a larger current produces a stronger magnetic field.
Increase the number of turns of wire – each turn adds its own field, so more turns give a stronger overall field.
Add an iron core – the core provides a path of lower reluctance, allowing more field lines to pass through and increasing the field strength.
Use a higher‑conductivity wire or reduce resistance – this allows a higher current for the same battery voltage, further strengthening the field.
Increase the number of turns of wire – each turn adds its own field, so more turns give a stronger overall field.
Add an iron core – the core provides a path of lower reluctance, allowing more field lines to pass through and increasing the field strength.
Use a higher‑conductivity wire or reduce resistance – this allows a higher current for the same battery voltage, further strengthening the field.
Examiner tips
- Use the word ‘increase’ and explain the physical reason for each method. Mention the relationship B∝nI and the role of the core’s permeability. Keep each explanation concise and to the point.
Common mistakes
- Confusing the number of turns with the length of the solenoid. Failing to mention that the core must be ferromagnetic. Using vague phrases like ‘make it stronger’ without explaining why.
Mark scheme (4 marks)
- Increase the current through the solenoid
- Because a greater current produces a stronger magnetic field
- Increase the number of turns (coils) of wire / add more coils
- Because each additional turn contributes its own magnetic field, so the fields combine to produce a stronger overall field / adding an iron core allows field lines to pass through more easily than air, increasing field strength
Key terms in this question
Related
- All Edexcel GCSE Physics (1PH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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