A dielectric inserted between the plates of a charged, isolated capacitor causes the potential difference to
- A. increase
- B. decrease, because the capacitance rises while the charge is fixed
- C. stay the same
- D. become zero
Explanation
With the capacitor disconnected the charge cannot change, and since V equals Q over C, raising the capacitance must lower the voltage. The dielectric molecules polarise and set up a field opposing the original one, which is the physical reason for the drop. If instead the capacitor stayed connected to a battery, the voltage would be fixed and the charge would rise.