Capacitance question?

Question

A parallel plate capacitor in a vacuum has a capacitance of 6.4 nF. The capacitor is fully charged by connecting it across a 128V voltage source. The voltage is then removed without discharging the capacitor, and the space between the plates is filled withe a dielectric material. the capacitance is measure again and found to be 28.8 nF

So i found that voltage across the plates is 28.44V after inserting the dielectric. And that the charge on the plates will remain the same 8.192*10^-7 C.

Suppose the dielectric was inserted before removing the voltage source. Will the charge on the plates increase, decrease or remain the same? and what is the voltage across the plates now?

So is voltage across the capacitor stay the same as well then? So it doesnt matter when the dielectric is placed between the plates?

Answer 1

There's the same amount of charge despite what you put between the plates. The capacitance/volts will change but the charge won't change if you mess with a charged capacitor. Q=CV rules.

Answer 2

Duh--- That should be obvious. Read your question again, slowly, if you are still have problems post again.pp