# Need help on electromagnetic poles and induced current

1. Feb 1, 2014

### vearnwong

Hello, I know the magnetic field produced by a direct current flowing through a solenoid has a north and south pole, so how about the magnetic field produced by a current flowing through a straight conductor, does it have a north and south pole too? If it have them, where is it located?

A changing magnetic field can induce current in another conductor close to it, but how does it work actually? what energy is it that drive the electrons to produce the current?

Thanks.

2. Feb 1, 2014

### Staff: Mentor

No. A magnetic "pole" is simply a region where the magnetic field (as visualized by its field lines) diverges or converges. There is no such region associated with a straight wire.

According to Maxwell's equations, a changing magnetic field is associated with an electric field, which exerts an electric force on the electrons, causing them to move. The necessary energy ultimately comes from whatever mechanism is producing the change in the magnetic field. I suppose you can think of it as being "passed on" to the electrons via the energy stored in the electromagnetic field.

3. Feb 2, 2014

### vearnwong

Thanks a lot on the poles. That really clears things up.

About induced current, I'm still in a haze. I understand what you mean by passing on the energy as in the principle of conservation of energy, what I'm wondering about is does the changing magnetic field somehow able to cause an "imbalance" in the amount of negative charges which produce a potential difference or produce an attractive or repulsive force with the electric field of electrons which subsequently causes it to move.

I really appreciate the help as I'm having trouble finding the explanations on the web. Thanks.