Question

A Bar magnet has a magnetic moment M and length l. If its length is reduced to half, find its new magnetic moment.

Hint:

Remember the two ways to cut a magnet:
1. Transversely (perpendicular to length): length halves ($l \rightarrow l/2$), pole strength is constant ($m \rightarrow m$). $M' = M/2$.
2. Longitudinally (along the length): length is constant ($l \rightarrow l$), pole strength halves ($m \rightarrow m/2$). $M' = M/2$.
In both typical cutting scenarios into two equal pieces, the magnetic moment halves.

Answer 1