# Electromagnetics (solenoid question)

1. Apr 28, 2006

### dingpud

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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Thomas Midgley, responsible for leaded gasoline and the introduction of CFC's...ultimatley killed by his on contraption...poetic justice? :surprised

2. Apr 28, 2006

### dingpud

the hamster may have fallen off the wheel...

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

3. Apr 29, 2006

### Twukwuw

usually, the solenoid we study in university text books 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
$$B=\frac{\mu\NI}{L}$$
(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: Apr 29, 2006
4. May 1, 2006

### dingpud

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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