How do I compute the force acting on an uncharged shperical iron nugget in a magnetic field, as a function of mass and field strength?
How does it change with time if the iron starts with a zero net magnetic moment?
F=Q(E+VxB) E= electric field B= magnetic field V= velocity Q= charge of the ball
When the magnetic field comes from a circular wire around the ball: B= MI/2r M= 4x10^-7 I= electric current flow r = distance of the ball from the wireE=0
And then: F=QVxB
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The iron ball has zero net charge Q and zero velocity V. The force is created by the ferromagnetic property of iron (think fridge magnets...), and that's what I don't know how to derive.
According to what I know, only when Q is mooving there will be a magnetic force.
knownot: then what's keeping the magnets stuck to your fridge door? Everything there has a zero net charge (because your fridge is grounded, for one). In ferromagnetic materials such as iron there actually is something analogous to moving charge, at the atomic quantum-mechanical level. But I don't know how to analyze or quantify it.
When feromagnetic material is found in the magnetic field of a magnet, it turns into a temporary magnet (induced magnetism) of an opposite polarity magnets, so they pull each other.
The equation is: m = pd m= magnetic moment (the force) p= strength of its poles d= distance between them
(The equation is from wikipedia: http://en.wikipedia.org/wiki/Magnetic_moment)
This equation doesn't seem applicable: I don't know what's the strength of the amount of induced magnetism, I don't know what you mean by "strength of poles", and there is no relevant notion of distance. Also, I want to know how it all varies with time, since presumably the induced magnetism happens gradually as the magnetic domains in the iron align to the external field.
I am also trying to find a solution to this problem. F = qV X B is not applicable. From what I have found: The force on a dipole magnet is proportional to the dB/dX (gradient) or the change in the magnetic field. This is defined for a magnetic field that is uniform about the whole surface of the dipole/ferromagnetic material. This also defined for a dipole permanent magnet and not a magnetized ferromagnetic object though the two should be similar. I suspect that the truth is that the force on a dipole permanent magnet is proportional to the change in flux, not simply field, through the surface that would contact the field. Though this can't tell the whole story for a ferromagnetic material however or else this information would be a lot easier to find I think.
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