A solenoid is connected to a direct current (d.c.) supply. Describe the magnetic field produced inside and outside the solenoid, and explain how the strength of this magnetic field can be increased.

WJEC GCSE Physics (Wales) — 2.5 Magnetism and electromagnetism · Describe and Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

The field inside the solenoid is uniform, with field lines running parallel to the axis of the coil.
The field outside the solenoid resembles that of a bar magnet, with a north pole at one end and a south pole at the other.
The field strength can be increased by raising the current through the coil.
It can also be increased by increasing the number of turns per unit length of the solenoid.

Examiner tips

  • Use the terms "uniform" and "parallel field lines" for the inside field. Mention the bar‑magnet analogy for the outside field. Show the two ways to increase B: higher current and more turns per metre. Keep the answer concise to fit the 4 marks.

Common mistakes

  • Describing the inside field as "strong" without mentioning uniformity. Forgetting to mention the bar‑magnet analogy for the outside field. Failing to state both methods of increasing the field strength.

Mark scheme (4 marks)

  1. The magnetic field inside the solenoid is uniform (parallel field lines along the axis)
  2. The magnetic field outside the solenoid is similar to that of a bar magnet (with a north and south pole at each end)
  3. Increasing the current in the solenoid increases the strength of the magnetic field
  4. Increasing the number of turns (coils/loops) per unit length increases the strength of the magnetic field

Key terms in this question

solenoid · magnetic field · direct current

Related

More Magnetism and electromagnetism questions

▶ Try answering this question with AI marking (free) →