Magnetic Or Electric Field

[Little Bang]

Suppose I had a conductor that I could roll at a high speed under a vibrating sheet of paper and had iron fillings on the paper. Would the traditional field lines still show on the paper or would they be distorted by the spinning field?

[Little Bang]

I don't mean that the conductor rolls along under the sheet of paper. It stays in one place and rolls.

[joekgamer]

What field? Is the conducter magnetic?

[Little Bang]

The conductor has, let's say, fifty amps passing through it. That would make the field electric.

[joekgamer]

As far as I can tell, no. The coducter (which I presume is symmetrical) has the electrical charge spread evenly across its entire surface. So, because there is no dynamic electrical field (only a static one), the filings are unnaffected.

[Little Bang]

You mean if I gave the electron two different directions of motion the field is unaffected?

[joekgamer]

An electron cannot have 'two directions of motion'. The electrons in a wire move along the outside of the wire. If the electrons move in a straight line normally, then spinning the wire will cause the electrons to move in a spiral, but only when seen from outside of the wire. An observer in the wire will see the electrons continue to move in a straight line.

[Jay-qu]

I think you are a little confused with the concepts.

 

A moving charge will create a magnetic field. A current is a moving charge. So if your conductor has 50A passing through it, it will have a magnetic field circling it. This is not like a dipole magnet, so the magnetic filings will have a different shape from the traditional dipole shape you may be thinking of. The field lines will be straight across the paper and perpendicular to the direction of current in your conductor.

 

That been said, now we can ask the question of whether spinning the conductor will alter its magnetic field. As Polymath pointed to, the symmetry of the system does, at first glance, appear to leave the situation unchanged - but that doesn't have to be the case for a moving charge. Say you moved in a frame moving along with current, but not spinning. You would simply 'see' electrons spinning around a conductor, this type of movement seems analogous to the movement of electrons in a solenoid - but I am not convinced the situations are the same..

 

That said, pretending the correspondence is applicable - a solenoid produces a field parallel to its length and surface, like a dipole magnet. Depending on the speed of the rotation of the conductor, you would produce an extra field that will add to the existing field. In short, yes there should be a difference in the field but unless one of these components is much stronger than the other, it is hard to say exactly what the shape of the field would be.

[Little Bang]

Good answer Jay, that is how I see it too.