Magnetism
4 marks · NormalA bar magnet is placed under a piece of paper. A student sprinkles iron filings above and observes the pattern formed.
Describe what the pattern of iron filings reveals about the shape and strength of the magnetic field around the bar magnet.
The student now arranges two bar magnets 3 cm apart so their opposite poles face each other.
Explain how the iron filings' pattern will be different in the space between the magnets. What does this show?
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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(a) The iron filings form curved lines from the north to south pole. Filings are closer together where the field is strongest (near the poles) and more spread out where it is weaker. · must show Curved pattern from north to south, Closer filings = stronger field, More spread out = weaker field
(b) Between opposite poles, the filings create mostly straight, evenly spaced lines, showing a uniform field with constant strength and direction. · must show Straight, parallel lines between magnets, Uniform field
Common mistakes: Not describing strength in terms of spacing; Missing the straight/parallel lines for uniform field
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Marking points
B1 (a) · 1 mark · Describes curved field lines from north to south around magnet.
B2 (a) · 1 mark · States filings are closer where the field is stronger (near poles).
B1 (b) · 1 mark · Describes straight or parallel lines between the two magnets.
B2 (b) · 1 mark · Correctly states this is a uniform magnetic field.
Worked solution
(a) The iron filings form curved lines that show the magnetic field going from the north to the south pole. The lines are closest together at the ends (poles) where the field is strongest. They spread apart in regions where the field is weaker.
(b) With opposite poles facing each other, the filings between them will form almost straight and evenly spaced lines. This shows a uniform magnetic field (constant strength and direction) between the poles.