Question

If two bar magnets of different magnetic lengths have equal moments, then the pole strength is :

• A. equal for both the magnets
• B. less for shorter magnet
• C. more for longer magnet
• D. more for shorter magnet

Answer 1

The correct option is D more for shorter magnet

Magnetic moment of a magnet = $ml$
where
$m=$ pole strength
$l=$ effective distance between the two poles
Therefore if Magnetic Moment is kept constant, the pole strength is inversely proportional to the effective distance between the poles.