Splitting a bar Magnet Lengthwise
Most recent answer: 03/21/2010
- Michael French
Napavine Washington, U.S.A
The other way of looking at it, a bit more obscure perhaps, is that there is an energy density associated with magnetic fields. It's a bit complicated but the essential point is that the total energy is proportional to the square of the magnetic field integrated over space. The total energy of the two halves put together is more than twice the total energy of the two halves separated far apart. So there will be a force pushing them apart.
(published on 03/21/2010)
Follow-Up #1: when do broken magnets repel?
- paul (age 62)
Two magnets placed side-by-side repel if their fields point the same way. Placed end-to-end, they attract if the fields point the same way.
For bar magnets, it's true that if you break them in half across the small dimension, the halves attract, If you break them in half lengthwise the halves repel unless you line them up end to end.
The magnetic field in your broken magnet must have pointed approximately in the plane of the broken surface.
(published on 07/14/2013)