What Causes a Magnetic Field in a Wire?

In summary, Hans Christian Oersted discovered that an electric current creates a magnetic field, which is caused by the length contraction of electrons.
  • #1
icesalmon
270
13
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?
 
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  • #2
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
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
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
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
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.
 

What is a magnetic field?

A magnetic field is a region in space where magnetic forces are exerted on objects with magnetic properties. It is created by the movement of electrically charged particles, such as electrons.

How does a wire create a magnetic field?

When an electric current flows through a wire, it creates a magnetic field around the wire. This is because the movement of the electric charges in the wire creates a circular magnetic field around the wire.

What is the direction of a magnetic field in a wire?

The direction of a magnetic field in a wire is determined by the direction of the electric current. The field lines will always form circles around the wire, with the direction of the field determined by the right-hand rule.

How can the strength of a magnetic field be increased in a wire?

The strength of a magnetic field in a wire can be increased by increasing the current flowing through the wire, increasing the number of loops in the wire, or by using a material with higher magnetic permeability.

What are some applications of magnetic fields in wires?

Magnetic fields in wires have various practical applications, such as in electric motors, generators, and transformers. They are also used in technologies such as MRI machines and maglev trains.

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