Discussion Forum

Dear COMSOL users,

I am working on my thesis and currently I have some questions regarding electric field line distribution in COMSOL.

Firstly, I went through the COMSOL document for choosing the correct physics (ec and es). I have parallel plate across a sphere immersed inside a liquid (can be seen in the attachments). The liquid has conductivity of 1.4S/m and relative permittivity of 60, while sphere has conductivity of 0.5S/m and relative permittivity of 80. Their relaxation times (tao=eps/sigma) are higher than 42.85. Our signal frequency is 500kHz (I am not sure what is the external time `t` that I should use, but I am assuming that it might be the period of the signal).

I tried electric currents physics first and realized that the electric field lines only depend on the conductance of the materials used, nothing to do with their permittivities. I couldn’t understand why this is the case.

Also, I tried electrostatics physics which does not need conductance information. It only changes with permittivity, which is the opposite case of the previous paragraph. In that case I had a result which is different than what is written in the MIT web page (attachments: COMSOL electrostatics and MIT permittivity[figure b]). Electric field lines are diverging as expected but they are continuous on the boundary and less dense than expected. How can I simulate a "non-continuous" electric field lines on the surface of the sphere which will have a result similar to the theory?

Link for MIT source: web.mit.edu/6.013_book/www/chapter6/6.6.html

Thank you for your support.