# Electromagnets and pole shifting

1. Jun 16, 2007

### Mr_Bojingles

I read a couple of tutorials on electromagnetism and solenoids but theres a good few questions left unanswered.

1.) What determines the poles of a solenoid electromagnet? Lets say I have direct current flowing from the left end of the coil to the right. Will the north pole automatically be on the left end of the solenoid or the other way around?

If I turn the battery around will that reverse the poles?

2.) Say I have a long circuit with the wires places side by side so the two wires run parallel. Lets say theres a heavy current running through the circuit.

Battery================Resistor

Since theres a small magnetic field surrounding the wire through the whole circuit and the wires are close enough that their magnetic fields overlap. Would it create 2 poles one at the battery end and one at the resistor end?

2. Jun 16, 2007

### Danger

This site might cover everything that you want to know. I didn't check it all out, but the beginning is good. Your 2-wire problem, as far as I know, isn't a problem at all. If they are following the same path, they essentially act as one larger wire. That's how stranded cables work.
http://library.thinkquest.org/13526/c3c.htm"

Last edited by a moderator: Apr 22, 2017
3. Jun 17, 2007

### NoTime

1) Depends on which way the coil is wound.
Look up the right hand rule.

1A) Yes.

2) What does the field look like around a single wire?
Using the right rule, what is different about the field on wire A and the field on wire B.
What do you think happens when you overlap the two fields?

4. Jun 17, 2007

### NoTime

The current will be going in one direction in one wire and the reverse direction in the other wire.
If the current was going the same direction in both wires then you would be correct.

Last edited by a moderator: Apr 22, 2017
5. Jun 17, 2007

### Danger

Ooops! Sorry, I misunderstood the question. I didn't realize that he meant that the second wire was the return path.