Question

what is the s.i unit of a) pole strength and b)magnetic moment of a bar magnetic moment

Answer 1

The unit for magnetic moment in terms of the International System of Units (SI) base units is A. m2, where "A" is the ampere (the SI unit of current) and "m" is the meter (the SI unit of distance).

Answer 2

1. Pole strength is the amount of force a pole of magnet exerts when another magnet of opposite polarity is brought near it.

Pole Strength=Work Done in moving a magnet around a wire/current in the wire

P=W/I.

Unit of Work is Joules(J) and that of current is Ampere (A).

Joules/Ampere=Weber

So the unit of pole strength is Weber(Wb).





2.


If m is magnetic pole strength and 2l is distance between them, the magnetic moment M =2ml.

It is clear that cutting the bar magnet in two equal parts ,each half will have magnetic moment =M/2. This is because, cutting the bar magnet in pieces , it's pole strength does not change.( if the cut is perpendicular to the axis of bar magnet.)

A solenoid also behaves like a bar magnet. If current I is passing through a solenoid of length l with n turns per unit length and area of cross section ,A, the magnetic moment of the solenoid is

M=nl IA.

So , cutting this solenoid in two equal halves ,each half will have magnetic moment = M/2.