4. The potential difference between the plates of a flat capacitor is 900 V. The capacitance of the capacitor is 200 pF. The space between the plates of the capacitor is filled with glass with a dielectric constant ε = 6. What work must be done to remove the glass from the capacitor, after disconnecting it from the voltage source? (Friction neglected).

Detailed solution. Decorated in Microsoft Word 2003. (Target decided to use formula editor)