Strange behavior of capacitor

Okkkk. I got it ,thanks

Nothing strange. Just high electrostatic voltage when capacity is decreased created by homeless electric charges throwed out of cap and when they try to establish route to next nearest possible neutralization point such as ground ifnwebtal about negative ones or atract oposite charges when they are positive charges on second cap plate . This create almost ideal current source behavior so when a resistance is on the route voltage will be created by this charges of such magnitude to makes travel possible(and in the energy available limit to cover resistance loses). Ofcoz this happens when u decrease capacty of alredy charged cap. Doing this on empty one theoreticaly create no voltage response. This is crucial phenomenon that makes parametrical amplification possible. If variable capacitance device (varactor for example) posses electric control posibility then became an Active device such as transistor or tube. Electromechanical solutions also exist (for example a '"Dynamic capacitor") in modern design cap is varied by change of plate distance by piezoelectric means older such devices vary plate ditance by moving electromagnet. and rather are obsolete now.

Thats exactly how a capacitor microphone works. The sound moves one of the plates changing the capacity. The sound energy is converted to a change of voltage which is then processed by an amp.