Question

I partially get it but don’t completely understand what is weird about it. Please tell me what I’m getting wrong.

Lets say North(stronger) is on the top and South on the bottom.

I understand the next two bits:

Dipoles entering perfectly aligned with north(top) south(bottom) will be deflected down by the maximum amount. (or will they just rotate 180 degrees and deflect up?)

Dipoles entering perfectly aligned with south(top) north(bottom) will be deflected up by the maximum amount.

What I don’t understand is why dipoles entering at angles e.g. north(45 degrees from top) don’t immediately align themselves with the magnetic field like a compass needle would, and then proceed as 1) or 2) and therefore, all end up with the maximum deflection?

All the explanations I’ve seen seem to think the dipole should not align itself north-south, and should therefore only deflect partially (filling the gap in the middle).

What’s the reason that the dipole can’t align itself north-south?

A) moving too quickly – it’s out of the magnet before it can turn?

B) Angular momentum (Larmor precession) resisting the turning force?

C) something else?

Or have I got this completely wrong and the dipole does align itself, but the quantization isn’t to do with the direction of the angular momentum, but the magnitude of it?

Were they expecting the magnetic dipole moments to have random magnitudes (and thus be deflected proportional to the magnitude)?

Does the angular momentum play any part in this experiment, or does it just produce the magnetic dipole moment?

Answer 1

Magnetic dipoles in a magnetic field do not always align due to angular momentum and Larmor precession. The type of material affects the dipoles' behavior, and quantization applies to both the direction and magnitude of dipoles' magnetic moments.

Step-by-step explanation:

The behavior of magnetic dipoles in a magnetic field is an interesting phenomenon in physics. When a dipole is placed in a magnetic field, we might expect it to align with the field just like a compass needle does. However, this expected behavior doesn't always occur due to other factors at play.

In the scenario you've mentioned where dipoles enter a field at an angle, the reason they don't always align with the magnetic field to achieve maximum deflection is due to factors like angular momentum and Larmor precession. These phenomena resist the turning force exerted on the dipole by the magnetic field. Moreover, the rapid movement of the dipoles might prevent full alignment before they exit the field. The alignment of dipoles in a material also depends on the type of material, as ferromagnetic materials can become permanently magnetized, while paramagnetic materials will only show magnetization in the presence of an external magnetic field.

The quantization observed in dipoles in an external magnetic field doesn't relate just to the direction of their alignment but also to the magnitude of their quantized angular momentum and the magnetic dipole moment this momentum produces. So, while a dipole's orientation does affect the magnetic dipole moment, the magnitude of this moment is also quantized.