# Discussion Forum

## Inconsistent Potential Over a Cylindrical Surface

Hi,

I made the following construction in COMSOL (This is a cut):

Two cylinders, the inner one in the middle is a solid cylindrical conductor. The thick outer cylindrical shell, along with the two small cylinders above and below the even smaller middle one, represent air.

I set the space charge density of the conductor (the small cylinder in the middle) to 1 C/m^3, I then applied a tetrahedral meshing to the conductor and a swept mesh to the surroundings. After running the simulation, I was interested in the potential over the surface of the conductor, here's what it looked like:

There is clearly an inconsistency in the plot above, since the potential is constant over the surface of a conductor, the plot should be monochromatic.

Here are some screenshots that might be helpful.

Any help would be more than welcome.

2 Replies Last Post 3 Sep 2019, 19:32 GMT-4

Posted: 5 months ago
Updated: 5 months ago

Hello Steven,

The wide range of colors is misleading you. Check out the color bar: all colors correspond to essentially the same value (The values are all within .1% of each other since 3 digits are displayed here).

Best regards,

Jeff

-------------------
Jeff Hiller

Posted: 5 months ago
Updated: 5 months ago

Thank you Jeff,

Indeed, after running additional tests, the potential seemed to be constant over the whole surface and within, and its value was exactly equal to the one shown on the colorbar, i.e., .

Regards,

Steven