Sign up ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free.

When sliding a magnet over a ferromagnetic surface there is no magnetic force at all, however,there is a magnetic force only at the edge, when the magnet is being pulled of I assume the magnetic field is trying to resist. However, a fact it noticeable, the sliding/lateral magnetic force at the edge is a lot less, by a factor of half - ten times less.

What could be the reasons that detains the magnitude of the lateral force? Pelase do explain in detail.

Thank you.

share|cite|improve this question

1 Answer 1

attractive magnetic force is perpendicular to the movement of the magnet until the magnet moves past the edge of the ferro metal--then the force suddenly becomes opposite to the direction of movement.

share|cite|improve this answer
Why? How could the force initially be 0, only at the edge it applies a certain value? I know the magnetic field is trying to pass through that ferro metal instead of air, but how can it apply a lateral force? – M.A Sep 5 '13 at 16:18
draw a diagram of a magnet sitting on a sheet of ferro metal and note the magnetic field direction. then draw the magnet at the same height but now just off from the edge. it should be obvious why you only notice a large resistance when the magnet leaves the edge. also, it's not true that the initial force is zero. because it is downwards it causes increased friction between magnet and metal as you drag it. but friction is only a fraction of the perpendicular force (coefficient of friction principle) so when the magnet leaves the edge friction drops to zero but now magnetic resistance is max – gregsan Sep 5 '13 at 19:45
Do explain how it's obvious? Btw, magnetic force at the edge can not be at it's max, in fact, it's at the lowest. Compare it with magnetic pull force that is perpendicular to the surface it's not even close to it. – M.A Sep 6 '13 at 4:13
the direction of magnetic force is different. it is maximum with respect to the direction of motion of the magnet when the magnet is just off the edge – gregsan Sep 6 '13 at 14:58
Ah, by you saying with respect to the motion, you mean going laterally the MAX force is different that the pull force(perpendicular to the surface). Is there a possible way to decrease the lateral force? While trying to slide off the magnet? – M.A Sep 6 '13 at 18:23

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.