Discussion Forum

Hi all,

I am an entry-level person seeking to model a parallel plate capacitaor.
Basically I have built two plates (two electrodes) in parallel. One is set with positive voltage (for eg: 1V), another plate I set as grounded. These two parallel plates were covered by a bigger box (I set this box material as one dielectric material with dielectric constant around 4). I used the global evaluation and got the capacitance which was much larger (almose doubled ) than my theroretical value (for theoretical vale I use the formula as e0er*surface are/dielectric film thickness ). Then I changed the surrounding material ( the big box material) of two electrodes to Air while the materials between these electrodes remain as same before. Then, the simulated value was close but still with small error compared to theory. So there are some questions raised in my head: Why the error is so big when the electrodes was covered by the dielectric materials (eg: Glass (NOT AIR)). When I changed it to air, why the capacitance still not the same value as the theoretical one?

Secondly, I changed the electrodes voltage. The first electrode was applied with 1V positive voltag as before while the second electrode was changed from grounded to -1V. Then I checked the simulated capacitance which is doubled as the pervious capacitance ( with one electrode grounded nd one electrode positive voltage). Why is that doubled? If this value is wrong, how should I simulate the capacitance in this case?

It will be very much great helps and thanks for any reply or suggestion!

Thanks again.