Will a current loop precess or align with a magnetic field?

In summary, the conversation discusses the behavior of a current loop in an external magnetic field. It is mentioned that the torque from the magnetic field will cause the loop to align with it, but the question arises whether or not this alignment will result in precession. It is suggested that precession may not occur due to the small mass and slow movement of the electrons in the wire, but the possibility of precession in a superconducting loop is also brought up.
  • #1
nonequilibrium
1,439
2
Hello,

When I have a current loop (macroscopical, but I don't know if that matters) in an external magnetic field such that the loop's magnetic moment vector is not aligned with the magnetic field, I know it'll create a torque on the loop to align it with the B-field. I was wondering: does this torque always imply precession, or will we simply see alignment in real life? Are there extra conditions that need to be specified before you can say if there will be noticeable precession or alignment?

Thank you.
 
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  • #2
It will align in the direction that has the least energy (with the field). It won't keep rotating due to friction, and in an ideal situation it might oscillate but I haven't though about how this motion affects the current in the loop (if it is significant).
 
  • #3
How come precession doesn't come into the picture?
 
  • #4
you need angular momentum to have precession
 
  • #5
granpa - exactly, the electrons in the wire?
 
  • #6
they have very little mass and they move very slowly
 
  • #7
Hm, the argument of "very little mass" doesn't seem valid, because they also have "very little charge", but they're massive in numbers. I suppose the "moving very slowl" argument could make sense... (but not sure because the current itself, after all, is not slow, so the mass movement of the charges/masses also isn't slow). But would you then say that a superconducting loop would precess? Because there the charges don't continuously (they never) bump into things and thus should go a lot faster.
 

1. Will a current loop precess or align with a magnetic field?

The motion of a current loop in a magnetic field depends on the orientation of the loop and the direction of the current. If the loop is parallel to the magnetic field, it will align with the field and experience no precession. If the loop is perpendicular to the field, it will precess around the field lines.

2. What is precession in a magnetic field?

Precession is the circular motion of an object around a fixed axis due to the influence of a magnetic field. In the context of a current loop, it refers to the circular motion of the loop around the magnetic field lines.

3. How does the strength of the magnetic field affect the precession of a current loop?

The strength of the magnetic field has a direct impact on the precession of a current loop. A stronger magnetic field will result in a faster precession rate, while a weaker field will result in a slower precession rate.

4. Can the direction of the current affect the precession of a current loop?

Yes, the direction of the current in a loop can impact its precession in a magnetic field. If the current is in the same direction as the field, the loop will align with the field and experience no precession. If the current is in the opposite direction, the loop will precess in the opposite direction.

5. Is the precession of a current loop affected by the shape of the loop?

Yes, the shape of the loop can affect its precession in a magnetic field. A circular loop will experience a uniform precession, while an elliptical loop will experience an uneven precession, with the narrower side precessing faster than the wider side.

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