Discussion Forum

I am new to COMSOL, having only attended a free workshop a number of months ago. I want to model an oscillating capacitor. One plate of the capacitor needs to oscillate at a specific frequency while the other plate remains still. Of course this will create a varying capacitance as the distance between the plates changes with oscillation.

To try to understand how to get started with this I have been looking at the capacitor_tunable.mph model under the AC/DC Module > Electrical Components. This seems to be a good place to start as the model library states;

"In an electrostatically tunable parallel plate capacitor you can modify the distance between the two plates when the applied voltage changes. For tuning of the distance between the plates the capacitor includes a spring that attaches to one of the plates. If you know the characteristics of the spring and the voltage between the plates, you can compute the distance between the plates. "

However the model library help doesn't discuss the separation of the plates after this. In my attempts to change the distance between the plates by changing the applied voltage(Physics>Boundary Settings>Groups>(unnamed2)>Vin), I don't seem to be getting changes in the solution. For example when plotting the global variable 'C11_emes' under Postprocessing it is always ~0.09pF regardless of the applied voltage. How can I view the change in distance between the two plates after solving the problem? What equation under Physics is controlling the distance between the plates? Where is the spring equation?

Of course after I understand this model a little better I will have to make my own which makes one of the plates oscillate at a particular frequency. Any suggestions you have around doing this are greatly welcomed.