Spin Coil in EM System for DC Current?

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Discussion Overview

The discussion revolves around the interaction between a coil of wire (assumed to be a solenoid) and a solid cylinder of magnetic material when subjected to a DC current. Participants explore the implications of spinning the outer cylinder and whether it would induce motion in the inner coil, considering concepts of magnetic coupling and torque.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether spinning the outer magnetic cylinder would cause the inner coil to spin, initially suggesting that the magnetic forces would remain unchanged regardless of the cylinder's motion.
  • Several participants agree that due to the axial symmetry of the iron shell and the solenoid's magnetic fields, there should be no torque generated when they spin relative to each other.
  • Another participant expresses a need to further investigate the concept of magnetic coupling in this context.
  • One participant suggests considering alternative configurations, such as using a magnet or electromagnet for the outer cylinder, while still questioning if this would alter the symmetry and resulting interactions.

Areas of Agreement / Disagreement

Participants generally agree on the idea that the axial symmetry of the system results in no torque when the outer cylinder spins relative to the inner coil. However, there is ongoing exploration of alternative configurations and their potential effects, indicating that the discussion remains open-ended.

Contextual Notes

Participants have not fully resolved the implications of different configurations, such as using a magnet or electromagnet for the outer cylinder, and how these might affect the system's behavior.

Who May Find This Useful

This discussion may be of interest to those studying electromagnetism, magnetic coupling, or mechanical systems involving rotational dynamics in electromagnetic contexts.

ehilge
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You have a coil of wire inside a solid cylinder of iron or some other magnetic material. There is a DC current going through the coil of wire so you have an electromagnet. If you were to spin the outer shell, would the coil also spin in the same direction.

My first thought when approaching this was no because the magnetic force between the coil and cylinder is the same in the either outward or inward. Essentially, you can spin it all you want but it won't change to force on the inner coil. However I don't think this is correct. The way I came across this situation is someone explaining the properties of a magnetic coupling to me. Essentially, you could have a motor driving the cylinder, and this would put torque on the inner coil which would spin whatever you want to drive. By changing the current through the coil, you can control how fast whatever you're driving rotates. So, I'm pretty sure I'm misunderstanding either the design or the principle. Your thoughts?
Thanks
 
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Your intuition is correct. Because the iron shell is axially symmetric, and so are the fields from the solenoid, there should be no torque when they spin relative to one another.
 
marcusl said:
Your intuition is correct. Because the iron shell is axially symmetric, and so are the fields from the solenoid, there should be no torque when they spin relative to one another.

curious, I guess I'll have to look into my magnetic coupling in a bit more detail.

thanks
 
I'm assuming that your coil of wire is a solenoid that is aligned with and located on the axis of a hollow iron cylinder.
 
marcusl said:
I'm assuming that your coil of wire is a solenoid that is aligned with and located on the axis of a hollow iron cylinder.

Correct. Any thoughts on how you could possibly transfer power in something like the arrangement I described. What if the outside cylinder was a magnet or electromagnet? I still don't think that would change anything because of the symmetry. Any other ideas?
 

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