Torques between revolving magnet bars

[Jackson Lee]

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??

 

[Andrew Mason]

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

 

[Jackson Lee]

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.

 

[Andrew Mason]

Good question, though. I had to think about it.

AM

 

[Jackson Lee]

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.

 

[Jackson Lee]

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