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Electric Field outside of a conducting sphere

Posted Jul 18, 2011, 3:54 p.m. EDT 3 Replies

Josh Lipsmeyer
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I'm very new to Comsol, and to be honest, my physics is a little rusty. I have two point potentials of equal and opposite value inside a conducting sphere. I am trying to calculate the E-field outside of the sphere. My geometry consist of 2 spheres, one inside of the other. The inner sphere was given characteristics of Copper and the outer sphere that of air. I placed a point potential along the x-axis and one of equal and opposite value in the center. I have attatched my model.

Josh

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3 Replies Last Post Jul 19, 2011, 12:57 p.m. EDT
Edgar Kaiser
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Posted: 1 decade ago Jul 19, 2011, 3:44 a.m. EDT
Hi,

I cannot open your model, because I am still on 4.1, but in general:

You won't see an electric field outside the conducting sphere with charges or potentials just inside.

Cheers
Edgar
Hi, I cannot open your model, because I am still on 4.1, but in general: You won't see an electric field outside the conducting sphere with charges or potentials just inside. Cheers Edgar
Edgar Kaiser
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Posted: 1 decade ago Jul 19, 2011, 7:00 a.m. EDT
I should correct myself: you will see the field of a sphere with the total charge inside. With two charges of equal magnitude and opposite sign the total charge is zero, i.e. no field outside.
I should correct myself: you will see the field of a sphere with the total charge inside. With two charges of equal magnitude and opposite sign the total charge is zero, i.e. no field outside.
Josh Lipsmeyer
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Posted: 1 decade ago Jul 19, 2011, 12:57 p.m. EDT
Makes sense. Thanks! What about the magnetic field of a line current in the sphere. Suppose I have an edge of current extending from some Z_0 to Z. I want to determing the Magnetic field inside and outside of the sphere, but I can't get the solution to converge. I am using the same geometry as before, which is a conducting sphere inside another sphere. I have a line from Z=.7 to Z=0. I am adding infinite elements to the domain outside of the conducting sphere. I have tried adding a transition boundary condition to the boundaries of the conducting sphere, but have failed in converging on a solution. It seems to me like this should be a simple model but I am having no success. Any suggestions?
Makes sense. Thanks! What about the magnetic field of a line current in the sphere. Suppose I have an edge of current extending from some Z_0 to Z. I want to determing the Magnetic field inside and outside of the sphere, but I can't get the solution to converge. I am using the same geometry as before, which is a conducting sphere inside another sphere. I have a line from Z=.7 to Z=0. I am adding infinite elements to the domain outside of the conducting sphere. I have tried adding a transition boundary condition to the boundaries of the conducting sphere, but have failed in converging on a solution. It seems to me like this should be a simple model but I am having no success. Any suggestions?

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