# conceptual understanding of electromagnetism

#### PG1995

Joined Apr 15, 2011
823
Hi

I understand that this is a very complex topic but we will try to keep it simple and uncomplicated! Thanks.

It is said that electrons in themselves are the reason for magnetism. As is explained in the linked page that if an electron is moving CW if viewed from the top, then electron's top is North and bottom is South.

I have a couple of questions to ask but asking them in steps would be a wise choice. In the first place I don't understand how we get circular magnetic field lines around a conducting wire. I understand that when DC current is flowing through a conductor electrons are continuous moving in one direction. But how do their collective movement create circular field lines?

This is how electron's magnetic field looks: Could you please refer me to some diagram etc. which shows how electrons' magnetic field sums up to give circular lines, or explain it yourself?

Magnetic field lines around a wire: Regards
PG

#### steveb

Joined Jul 3, 2008
2,436
I think using the magnetic field of the electron in your figure is misleading when talking about macroscopic fields, which is typical in electrical engineering. Magnetic moments of fundamental particles is important in physics but generally is not important for basic conduction of electrons and magnetic fields in wires.

However, if we replace the electron in your figure with a small length element of current, we get a fundamental magnetic field pattern. This field pattern becomes the basis for using the Biot Savart law which is the analog of Coulombs law when we do basic magnetic field calculations.

So just as we can calculate the total electric field by adding up all the fields of the point charges in a system, we can calculate the total magnetic field by adding up all the fields of the current elements in a system.

The following lecture talks about this in a detailed way, but note that the lecturer makes a mistake when she says that Faraday's law can be used in symmetrical cases. It is actually Amperes law that is used in those cases.

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