Are ALL parallel plate capacitors linear?

[lonelypancreas]

Homework Statement

Are ALL parallel plate capacitors linear?

Homework Equations

D = permittivity * E

The Attempt at a Solution

Capacitance is linear if permittivity is constant. Is there a case where a parallel plate capacitor is not linear?

 

[TSny]

http://www.ferrodevices.com/1/297/files/Chapter3-ParaelectricCapacitors.pdf

 

[berkeman]

http://www.ferrodevices.com/1/297/files/Chapter3-ParaelectricCapacitors.pdf

Interesting! I hadn't seen that before.

Capacitance is linear if permittivity is constant.

I'm not sure that's true... How exactly are you defining "linear" in this problem?

Is there a case where a parallel plate capacitor is not linear?

Have a look at the datasheets for some real capacitors (like tantalums). Do you see anything that might change your answer?