# Magnetic Field in a wire

1. Oct 22, 2014

### icesalmon

I'm learning about magnetism in my physics course, and we talked about Hans Christian Oersted's experiment where he observed electric current passing through a wire and analyzed the movement of a compass around this wire. He discovered that a magnetic field is generated by this current passing through the wire. But i'm confused about how exactly this magnetic field is generated though, we're told to just accept it. But it really irritates me. What exactly causes it? Why does moving charge create this field? Why does charge have to move through a solenoid or a wire to create this field? Is it important towards my understanding of magnetism?

2. Oct 22, 2014

### v3nture

Well, basically the electrons contain a charge and flow through the wire. When you wrap a wire around something like an iron nail and hook the wire up to a battery, the electrons flow through and create a magnetic field. You can read more detail about it here http://en.wikipedia.org/wiki/Electromagnet#Physics but for a basic understanding of magnetism it's not incredibly important unless your studying physics in University or really want to know what's going on (which is probably helpful with understanding the basic stuff as well). I think the link will answer your question better then I can.

3. Oct 22, 2014

### icesalmon

but HOW does that interaction create a magnetic field? What you've told me is what my professor told us, the link explains electromagnets but I didn't read it thoroughly enough to see if it answers my question. It's the interaction between electric charge flowing through a wire and the aligned field within the iron, I suppose because it's ferromagnetic? I'm still looking for something deeper, I wonder if it's more of a chemical thing

4. Oct 22, 2014

### Staff: Mentor

A magnetic field can be understood as a consequence of Coulombs law in conjunction with special relativity.

I am not sure if that will actually help you understand anything, but it seemed to be the kind of response you were asking for.

5. Oct 22, 2014

### Staff: Mentor

The underlying explanation involves a few concepts from Special Relativity. A full understanding would require you to understand SR completely, but the basic idea is that the moving electrons are length contracted when seen from a frame of reference that is in motion relative to the circuit. This length contraction makes the wire look like it is electrically charged, which will attract or repulse electric charges.

You can see the following link for more information, but be warned, it is not easy to understand completely.

http://en.wikipedia.org/wiki/Relativistic_electromagnetism

6. Oct 22, 2014

### icesalmon

this is much more of the kind of response I'm looking for, although I don't know an ounce of SR. It helps to give me another direction to search, thank you.