Torques between revolving magnet bars

  • Context: Undergrad 
  • Thread starter Thread starter Jackson Lee
  • Start date Start date
  • Tags Tags
    Magnet Torques
Click For Summary

Discussion Overview

The discussion revolves around the behavior of magnetic fields and torques in relation to current loops and real magnets. Participants explore the alignment of magnetic dipole moments and the implications of using real magnets versus theoretical current loops, as well as questions regarding electromotive force (emf) and inductance in coils.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant notes that when an external magnetic field is applied to a current loop, the net torque aligns the loop's dipole moment with the field, raising questions about the differences when using a real magnet.
  • Another participant argues that the coupling of North and South poles results in magnetic fields being aligned in the same direction, not opposite, using the example of two coil magnets placed together.
  • A participant expresses confusion regarding the emf of a coil, questioning whether it is defined by the rate of change of flux or flux linkage, particularly in the context of internal inductance of a long straight line.

Areas of Agreement / Disagreement

Participants exhibit some agreement on the alignment of magnetic fields but also present differing views on the implications of using real magnets versus current loops. The discussion on emf and inductance remains unresolved, with varying interpretations expressed.

Contextual Notes

Participants reference specific scenarios and examples, but there are limitations in the assumptions made regarding the behavior of magnetic fields and the definitions of emf and inductance, which are not fully explored.

Who May Find This Useful

This discussion may be useful for individuals interested in electromagnetism, magnetic fields, and the principles of inductance in electrical engineering or physics.

Jackson Lee
Messages
77
Reaction score
1
Hey, guys, I find a interesting phenomenon. When an external magnetic field is applied on a current loop, the net torque will try to align the loop's dipole moment with the magnetic field.
And considering that electrical loops could be regarded as electromagnet, we change the current loop into a real magnet.However, at this time, the net external applied magnetic field try to align the magnet in the same line but the opposite direction with the applied field for opposite poles attract each other.
Why do this happen? Is there any problem to exchange current loop with a real magnet??
 
Last edited:
Physics news on Phys.org
The N-S coupling results in the magnetic fields of the two magnets being in the same direction - not opposite directions. Think of two coil magnets being placed together length wise. If the South pole of one is touching the N pole of the other you have a double the length coil magnet with the N at one and and S at the other. The magnetic dipole moments of each coil are all aligned.

AM
 
Andrew Mason said:
The N-S coupling results in the magnetic fields of the two magnets being in the same direction - not opposite directions. Think of two coil magnets being placed together length wise. If the South pole of one is touching the N pole of the other you have a double the length coil magnet with the N at one and and S at the other. The magnetic dipole moments of each coil are all aligned.

AM
Thanks, I have got it.
 
Good question, though. I had to think about it.

AM
 
Andrew Mason said:
Good question, though. I had to think about it.

AM
Besides, I want to ask a another question. The emf of a coil is the rate of change of flux or flux linkage? Because I was totally confused by internal inductance of a long straight line, why we need only consider a fraction of total current.
 
Andrew Mason said:
Good question, though. I had to think about it.

AM
If you are free and interested in this topic, you can view this---https://[URL="https://www.physicsforums.com/threads/confusion-about-inner-inductance-of-transmission-line.802716/"]www.physicsforums.com/threads/confusion-about-inner-inductance-of-transmission-line.802716/[/URL]
Thanks very much
 
Last edited by a moderator:

Similar threads

Undergrad Magnetic dipole and a torque
  • · Replies 1 ·
Replies
1
Views
1K
Undergrad Charge movement relative to magnetic field frame dependence/invariance
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Expanding loop torque division
  • · Replies 3 ·
Replies
3
Views
414
Undergrad How induction works within a coil (nuances of it)
  • · Replies 6 ·
Replies
6
Views
2K
Undergrad The vector math of relative motion of wire-loop & bar magnet
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Does Larmor precession change the force exerted on a magnetic dipole?
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Work Done in Changing Shape of Current Carrying Loop
  • · Replies 5 ·
Replies
5
Views
2K
Graduate Larmor Precession and a bar magnet
  • · Replies 6 ·
Replies
6
Views
3K
Undergrad Structural difference between soft and hard ferromagnets
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Hall effect -- is it always applicable?
  • · Replies 7 ·
Replies
7
Views
3K