Electromagnetics (solenoid question)

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    Electromagnetics
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Discussion Overview

The discussion centers on the behavior of iron core solenoids when placed in close proximity to one another, particularly focusing on the interactions between their magnetic fields depending on the direction of the current flowing through them. The scope includes theoretical considerations and conceptual clarifications regarding magnetic field interactions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions how two solenoids placed side by side will interact, particularly if they have currents flowing in the same or opposite directions.
  • Another participant acknowledges the basic principle that magnetic fields will attract or repel each other but seeks clarification on whether solenoids behave differently in this context.
  • A third participant discusses the ideal properties of solenoids, noting that in an ideal scenario, two solenoids would not interact due to the negligible external magnetic field, while in a non-ideal case, they would behave like bar magnets and repel each other if the currents are in the same direction.
  • A later reply suggests treating solenoids as bar magnets for practical considerations, indicating a shift in approach to understanding their interactions.

Areas of Agreement / Disagreement

Participants express differing views on the interactions between solenoids, with some proposing that ideal solenoids do not interact while others suggest that non-ideal conditions lead to repulsion or attraction similar to bar magnets. The discussion remains unresolved regarding the specifics of these interactions.

Contextual Notes

Limitations include assumptions about the ideal nature of solenoids, the effects of air friction on motion, and the simplification of solenoids to bar magnets without fully addressing the complexities of their magnetic fields.

dingpud
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What happens when you place iron core solenoids in a row? The spacing between them would be minimal...I guess I'm looking for an answer to how each solenoid will act on the other. If the direction of the current in the solenoid is going the same direction for 2 side by side solenoids, the magnetic field is coming out of the same side of each solenoid. In the case that the current direction is reversed for one of the solenoids, obviously the magnetic field will be "coming out" of opposite ends, but would this change much?

I'm trying to remember if there is a coorelation to the effects of magnetic fields upon one another, but I can't seem to remember (or find) the relationship.

Any help would be appreciated.

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OK, I may have said something very redundant in the last thread. Obviously magnetic fields are going to repel or attract, but I wanted to know (in the case of a solenoid) if anything different would occur.

Thanks

dingpud
 
usually, the solenoid we study in university textbooks is ideal. That is, the diameter of the solenoid is very small compared to its length.
This ideal solenoid has one important property:

The magnatics field generated (when there is current) is "ALMOST" ZERO everywhere outside the solenoid.
In the solenoid, again, the condition of ideal means that:
The magnetic field is PARALLEL and uniform in magnitude.

Therefore, we have
[tex] B=\frac{\mu\NI}{L}[/tex]
(inside the solenoid)


Now I try to deduce what will happen when 2 solenoids are put together side by side.

If the solenoid is ideal (impossible in reality), the 2 solenoid will NOT interact. They will just remain stationary because the interaction is too weak and any motion will be impeded by the air-friction.
If the solenoid is not ideal, we modify the 2 solenoids as 2 magnet bars!
So, the question will be reduced to, what will happen when we put 2 magnet bar together!

Of course, they will repel each other, when the currents flow in the same direction.
 
Last edited:
Bar Magnets

OK, so I'm just going to treat the solenoids as bar magnets.

I'll post later if I ever get a chance to get any projects underway.

Thanks.

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