# Electromagnetism: Magnetic Field, change in permeability

Hello everyone.

I've built a Helmholtz coil and I'm attempting to understand how the magnetic field direction and magnitude will be effected do to a material with a particular permeability.

In the first picture I have an infinitely long cylinder with a particular thickness and permeability. There is a coil around the chamber. My Helmholtz coils are some distance from the chamber. I'm trying to find out how the B or H field is effected by the chamber due to its permeability and thickness. There are three areas that I'm concerned about. I was able to solve this for the center of the coil without the chamber using Biot Savart. I'm not sure what happens when a material is added in between.

In the second picture I have an infinitely long piece of square strut. The is a coil around the strut. The strut is off center to the coil. The strut has a particular height and width. I'm trying to find out how the be field is effected within the coils due to the piece of strut.

Is there a particular section in Jackson or Griffiths that would help me understand this problem? I'm assuming dB/dt = 0 as my coils have been turned on and running for some time.

Thanks to anyone who could provide some insight to this problem.

#### Attachments

• 4.9 KB Views: 358
• 3.4 KB Views: 341

Related Classical Physics News on Phys.org
mfb
Mentor
The cylinders in the sketch have infinite length, the coils do not (just two with zero length each)? I'm quite sure that needs a numeric simulation.

Assume just one coil in a plane. I'm pretty sure this will require a numeric simulation as well.

I found an example in Jackson that gives some insight to this problem. I have a CAD model of this. Is there is a free solver somewhere for a problem like this?

Have you access to any code solving the Laplace equation in 2D?
You should as a student. I can give you links if you need.