A steel ball bearing is held near a strong bar magnet but is not touching it. Explain why the ball bearing begins to move towards the magnet, and describe what type of force is responsible for this interaction.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A student places a steel ball bearing on a smooth surface approximately 5 cm away from a strong bar magnet. The student releases the ball bearing and observes it accelerating towards the magnet without any physical contact occurring.
Model answer (4 marks)
The bar magnet produces a magnetic field around it.
The steel ball bearing, being a magnetic material, is placed within this field.
Because it is inside the field it experiences a magnetic force.
This force acts without any physical contact, so it is a non‑contact force.
The resultant force is directed towards the magnet, giving the ball bearing a net acceleration in that direction.
The steel ball bearing, being a magnetic material, is placed within this field.
Because it is inside the field it experiences a magnetic force.
This force acts without any physical contact, so it is a non‑contact force.
The resultant force is directed towards the magnet, giving the ball bearing a net acceleration in that direction.
Examiner tips
- Use the term "magnetic field" and "magnetic force". Show that the force is non‑contact. Explain that the force causes acceleration. Keep the answer concise and to the point.
Common mistakes
- Confusing the force with a push or pull that requires contact. Failing to mention that the force is magnetic. Not linking the force to the resulting acceleration.
Mark scheme (4 marks)
- The magnet creates a magnetic field around it
- The ball bearing (as a magnetic material) experiences a force because it is within this magnetic field
- The force is a non-contact force because there is no physical contact between the ball bearing and the magnet
- There is a resultant force acting on the ball bearing (towards the magnet), so it accelerates in that direction
Related
- All Edexcel GCSE Physics (1PH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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