Discussion Forum

Are you talking about literally trying to use:
E=−∇Φ−∂A∂t
to compute Φ (i.e., the scalar potential field)?

Or, perhaps, do you simply want to compute (for example) the voltage between two conductors in a transmission line or comparable structure?

If the latter, then simply integrate the tangential component of E along a line connecting the two conductors and you'll obtain a voltage. If the former, then you may have to figure out how to extract the scalar potential field from the vector electric and magnetic fields. Good luck with that (and bear in mind that you'll have to decide what gauge you want to work in). Of course, if your problem is sufficiently low frequency that you can use the AC/DC module to solve for Φ and A, then it will be easier.

I don't know if that helps. You might want to post your specific problem & geometry to the forum.

Thanks for answering my questions.Your answer is very useful for my work.

What's more,I am calculating a resonant cavity's eigenfrequency in 2D model of frequency domain. I can't find the electric potential in postprocessing.Can I use the formula which you mentioned to get electric potential and how to set it in Comsol?

Thanks again for your kind help.

If you are computing a cavity's eigenfrequency, you are unlikely to have any use of the scalar potential field. The reasons you can't find the electric potential in the post-processing here is that it is not uniquely defined, nor is it likely to be useful. I encourage you to look in your EM/physics books about the relationships between the vector fields (E, H) and the scalar and vector potentials (Φ, A). Or see en.wikipedia.org/wiki/Magnetic_potential and en.wikipedia.org/wiki/Electric_potential and en.wikipedia.org/wiki/Gauge_fixing , among many, many other tutorial pages on the internet.

Thanks a lot for your answer.

Maybe my expression made you feel a little confused.Put it another way,if I have got electric field intensity in one plane,how to get electric potential by using comsol？

If you have a STATIC (or quasi-static) distribution of electric field, you can find the electric potential (to within a constant) via line integration. Start at a surface of known potential and do line integrals of - E dot dl (again, see en.wikipedia.org/wiki/Electric_potential ) from there to any point of interest. However, If you have an RF distribution of electric field (and that is exactly what you have in the case of the RF eigenvalue problem you mentioned), then it is a totally different matter. There is no unique scalar potential in that case because the curl of the electric field is non-zero. Again, I encourage you to see the other links I provided or consult an EM textbook. That's all the help I can offer.

I’m truly grateful for your help.

Best wishes for you.