Confusion about the nature of magnetic forces.

[siddharth5129]

Seeing as there is no net force on a magnetic dipole placed in a magnetic field ( only torque ) , and that magnetism in say a bar magnet is caused by nothing more than tiny atomic current loops ( magnetic dipoles) oriented in the same direction , i don't understand how a bar magnet would get attracted to say a refrigerator door, as this would require a net force as opposed to a net torque (Am i right in assuming that the bar magnet or refrigerator magnet magnetizes a certain area of the refrigerator door , and this area then sets up a magnetic field which influences the refrigerator magnet)

 

[jtbell]

There is no net force on a magnetic dipole placed in a uniform magnetic field.

 

[Bob S]

The Stern Gerlach experiment with a beam of neutral silver atoms in a magnetic field (~1923) with a gradient won the Nobel Prize in physics, because there was a force on the atoms..

[Edit] They won the Nobel Prize because there was a quantized force on the neutral atoms.
Bob S

 

[Bob_for_short]

The dipole potential energy U(r) in a magnetic field is -µB. If there is a space-dependence of B, i.e., B(r), then the -grad(U) is the force that makes work.

 

[SANGHERA.JAS]

No, magnetic field was only uniform along on plane. It was in fact placed in a way that magnetic field was in fact non uniform in certain direction. Otherwise gradient of field will be zero.