question about electric currents

[gib65]

From what I understand, electric currents create magnetism because electricity is a current of electrons and electrons are negatively charged causing magnetism. But then why wouldn't an object be magnetic at all times, even when there was no electric current flowing through it, since all objects have electrons (nevermind ionization)? What is it about electrons moving (giving rise to an electric current) that makes the object more magnetic?

[DV8 2XL]

Well they all have to be moving in the same direction, for a start. Also in some way everything does have a magnetic component, it just needs to be teased out with something like NMR.

[swansont]

Fields add, so you need unpaired electrons to end up with a net field in an atom.

[gib65]

Well they all have to be moving in the same direction, for a start. Also in some way everything does have a magnetic component, it just needs to be teased out with something like NMR.

 

Oh. How does moving in the same direction bring about magnetism?

 

Fields add, so you need unpaired electrons to end up with a net field in an atom.

 

What does a "net field" mean? Is that like saying the net amount of charge has to be negative? Is this what makes electricity magnetic - it constitutes a higher density of electrons?

[MattC]

First off, a net field:

Any magnetic field which you can feel or detect is really a combination of many tiny magnetic fields. In a magnetic metal, each atom in the metal is magnetic, and each atom generates a little field - they add up, together, to produce the magnetic field you observe in a magnet.

Non magnetic objects can have just as many magnetic fields, only the magnetic fields are all randomly directed. It's kind of like adding a bunch of +1's vs adding a bunch of randomly + or - 1's. In the case of the first you end up with a large number, eventually - the latter never yields a number.

 

Now, for your first question:

"Oh. How does moving in the same direction bring about magnetism?"

Actually, moving in the same direction is, in a sense, magnetism. When an electron orbiting an atom spins about the atom in it's orbital, it spins in a certain direction. As it moves, it generates a field, and that field moves along with it in the direction the electron spins. That field affects and is affected by other fields. If you have two electrons spinning in the same orbital and making fields, they will tend to align such that they cancel each other out - bringing the system to a lower state of energy (something nature very much desires). When you have an unpaired electron orbiting each atom, each atom has one electron orbital path that is not automatically canceled out by a pair. If you lock all of these individual orbital pathways into a certain direction, and keep that direction the same across all of the atoms in a bar of metal, that bar of metal becomes magnetic, due to the net force of all the individual and aligned electron orbital paths.

 

Some other things you should know:

Charges occur as either positive or negative, and opposites attract as much as two of the same charge will attract.

 

Two electron currents will attract each other if they are parrallel or in the same direction (as in two circles)

[s pepperchin]

First off' date=' a net field:

Any magnetic field which you can feel or detect is really a combination of many tiny magnetic fields. In a magnetic metal, each atom in the metal is magnetic, and each atom generates a little field - they add up, together, to produce the magnetic field you observe in a magnet.

Non magnetic objects can have just as many magnetic fields, only the magnetic fields are all randomly directed. It's kind of like adding a bunch of +1's vs adding a bunch of randomly + or - 1's. In the case of the first you end up with a large number, eventually - the latter never yields a number.

 

Now, for your first question:

"Oh. How does moving in the same direction bring about magnetism?"

Actually, moving in the same direction is, in a sense, magnetism. When an electron orbiting an atom spins about the atom in it's orbital, it spins in a certain direction. As it moves, it generates a field, and that field moves along with it in the direction the electron spins. That field affects and is affected by other fields. If you have two electrons spinning in the same orbital and making fields, they will tend to align such that they cancel each other out - bringing the system to a lower state of energy (something nature very much desires). When you have an unpaired electron orbiting each atom, each atom has one electron orbital path that is not automatically canceled out by a pair. If you lock all of these individual orbital pathways into a certain direction, and keep that direction the same across all of the atoms in a bar of metal, that bar of metal becomes magnetic, due to the [b']net [/b]force of all the individual and aligned electron orbital paths.

 

Some other things you should know:

Charges occur as either positive or negative, and opposites attract as much as two of the same charge will attract.

 

Two electron currents will attract each other if they are parrallel or in the same direction (as in two circles)

 

To try to add to this:

A charged particle has an electric field associated with that charge. Fields follow superposition rules so at a point in space we can sum the field vectors for all charges. This gives us the vector for the field at this point. A magnetic field is produced by a change in an electric field. The only way for the electric field to change is to move charges around (or add/subtract them from the system) what ever you do you are still moving them.

 

If you want more of an explanation look up Maxwell's equations on the internet.

[YT2095]

Hmmm... that goes part way to explain why metal detectors can pick up non-ferrous metals like gold or aluminium just as easily as iron or nickel then.

nice answers!