Magnetic Field of a Disk
Claimed by Andy Stevens (Spring 2018)
The Main Idea
Through this page, you will understand how to solve for the magnetic field produced by a moving charged, circular disk.
First, let us start with the basics. We know that moving charges spread out over the surface of an object will produce a magnetic field. This is similar to the concept of how charges spread out over an object allowed them to produce unique electric fields.
In order to figure out this magnetic field, we will start from the fundamental principles that we have learned already with regards to how magnetic fields are produced. We will then build on that and include the geometry of the object in question, in this a circular disk, in order to solve for the magnetic field produced by this disk.
A Mathematical Model
A disk can be considered as a collection of concentric current loops. Breaking the disk into a series of loops with infinitesimal width [math]\displaystyle{ dr }[/math] and with radius [math]\displaystyle{ r }[/math], we will have a total area of
[math]\displaystyle{ dA = 2\pi r dr }[/math]
And therefore have a total charge of
[math]\displaystyle{ dQ = 2\pi \sigma rdr }[/math]