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Magnetism And Matter

Question
CBSEENPH12037726

If the bar magnet in exercise question no 13 is turned around by 180°, where will the new null points be located?

Solution
When the magnet is rotated by an angle of 180o the neutral point will be on the equatorial line. If r’ is the distance of the neutral point from the centre of the magnet, then 

 μ04πMrB = 0.36 × 10-4 = μ04π2Mr3

 (r')3 = r32 

    r' = r21/3   = 14(2)1/3    = 11.1 cm 

The null point will be located on the normal bisector.