Creating a uniform magnetic field

3 marks · Normal

Describe how you could use iron filings and two bar magnets to show the difference between the field near the end of a single magnet and the field between two opposing poles. Include the expected patterns.

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

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Also accept: For a single magnet, sprinkle iron filings around one pole — filings curve outward, lines are denser near the pole and spread out. For two bar magnets with N and S poles facing, filings show straight, parallel lines between the poles. This shows the difference between non-uniform and uniform fields.

Common mistakes: Not specifying patterns for both situations; Confusing like poles with opposite poles.

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Marking points

M1 · 1 mark · Describes setting up iron filings around single and paired magnets correctly.

B1 · 1 mark · Correctly describes iron filings pattern near the end of a single bar magnet (curved, spreading lines).

B2 · 1 mark · Correctly describes iron filings pattern between two opposing poles (straight, parallel lines).

Worked solution

Sprinkle iron filings on paper over a single magnet; near a pole, filings show a curved, spreading pattern indicating a non-uniform field. Place two bar magnets with N and S poles facing each other closely, sprinkle filings — the filings in the gap show straight, parallel lines, indicating a uniform magnetic field.