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The work done in turning a magnet of magnetic moment M by an angle of 90° from the meridian, is n times the corresponding work done to turn it through an angle of 60°. The value of n is given by:

1. 2
2. 1
3. 0.5
4. 0.25

Correct answer: 2

Solution

The work done in turning a magnet in a uniform magnetic field is proportional to the difference in the cosine of the angles. For 90°, the work is proportional to (1 - 0), and for 60°, it is proportional to (1 - 0.5). The ratio is 2:1, so n = 2.

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