Current passing thru wire = mag field?

[nyaneko]

Why/How does a current that passes through a wire create a magnetic field?

 

[ProxyAmenRa]

A magnetic field is the instantaneous change in the electric field of a region. Electrons generate an electric field. As they move through a space the electric field changes resulting in a magnetic field.

 

[Cogwulf]

Magnetic fields are due to motion of electrons. Every electron has a tiny magnetic field, but in a piece of metal the motion of electrons is random so there is no overall field.
When you pass an electric current through the piece of metal, you force the electrons to move. The electrons are moving in the same direction, so there is some order between the motion of all the electrons. Because they are ordered, their magnetic fields add up to produce a net magnetic field.

 

[Jah]

I can tell you how you know what direction the magnetic field moves, if that helps.

(Though the explanation of why one appears requires a little deeper knowledge of the quantum model of electrons, and the quantum explanations of natural-magnetism.(ferromagnetism))

The trick is to point your thumb in the direction of the current, (negative to positive) and then the field induced will be in the direction your fingers are pointing.

Here; Imagine this is you, holding a wire through which a current is passing:

The current is passing in the direction of the arrows, to keep it simple.
Then the magnetic field will be rotating around the wire in this -> direction.
(note the small thumb in positive direction.)

 

[Cogwulf]

I can tell you how you know what direction the magnetic field moves, if that helps.

(Though the explanation of why one appears requires a little deeper knowledge of the quantum model of electrons, and the quantum explanations of natural-magnetism.(ferromagnetism))

The trick is to point your thumb in the direction of the current, (negative to positive) and then the field induced will be in the direction your fingers are pointing.

Here; Imagine this is you, holding a wire through which a current is passing:

The current is passing in the direction of the arrows, to keep it simple.
Then the magnetic field will be rotating around the wire in this -> direction.
(note the small thumb in positive direction.)

Don't forget it has to be your right hand.


I've been meaning to look into the quantum side to magnetism for a while, I study magnetism on my course but it's focused more on the materials and their properties than on magnetism itself.

 

[Latro]

Incidentally, the relativistic answer is that it DOESN'T, and that magnetism doesn't exist. Instead "magnetism" is what happens to the effect of an electric field which is being caused by a moving quantity of charge. That is, the underlying field still comes from the electrostatic force (as in stationary charges), but the effect of the field is changed by the fact that the particles are in motion. If I remember correctly the change is described exactly by a Lorentz transformation.

 

[nyaneko]

This is interesting, I guess there is no definite answer. Thanks for answering.

I do know how the direction they move, I'm in NZ and first year of university college, we learned that in highschool second year. I'm asking this just out of curiosity and boredom...

I have a guess that it's relative to the magnetic field of the earth....

Incidentally, the relativistic answer is that it DOESN'T, and that magnetism doesn't exist. Instead "magnetism" is what happens to the effect of an electric field which is being caused by a moving quantity of charge. That is, the underlying field still comes from the electrostatic force (as in stationary charges), but the effect of the field is changed by the fact that the particles are in motion. If I remember correctly the change is described exactly by a Lorentz transformation.

I'm not smart enough to understand that... sorry but I appreciate your great knowledge.

But what cogwolf and proxyamenra said is an answer I'm quite comfortable with...

 

[Jah]

Hint; It has to do with orientation of valence electrons in the shells. (which in a conductive metal are dislocated, and thus when they are externally effected will orient themselves (sorta) to mimic the ferromagnetic fields we find in natural magnets.)

( https://secure.wikimedia.org/wikipedia/en/wiki/Lanthanides#Magnetic_and_spectroscopic_properties and https://secure.wikimedia.org/wikipedia/en/wiki/Electron_shell )

 

[Vrecknidj]

Why/How does a current that passes through a wire create a magnetic field?

Magic.

 

[Latro]

I'm not smart enough to understand that... sorry but I appreciate your great knowledge.

But what cogwolf and proxyamenra said is an answer I'm quite comfortable with...

Sorry, without getting into the details of special relativity, the short version is that "magnetism" as a distinct force doesn't actually exist. Instead, when you move a particle that is creating an electric field (by virtue of being charged) sufficiently fast, its electric field gets changed significantly by relativistic effects. The changes result in the sort of phenomena that we commonly observe as magnetism.

This is actually kind of a big deal, because the classical magnetic force, unlike the classical electric force, has a very curious property: it's not conservative. This is a rather big deal if you think about it. Taking this relativistic perspective fixes that problem.

 

[Cogwulf]

Hint; It has to do with orientation of valence electrons in the shells. (which in a conductive metal are dislocated, and thus when they are externally effected will orient themselves (sorta) to mimic the ferromagnetic fields we find in natural magnets.)

Although conductive metals like copper tend to be diamagnetic and orient themselves opposite to applied fields.
Iron cobalt and nickel are the only ferromagnetic materials elements at room temperature, due to the spacing between atoms falling into the window where it can occur.

Coincidently, diamagnetism is a great way to confuse frogs

Spoiler

YouTube - ‪levitating frog‬‏

I just remembered I've got an exam on this tomorrow.