23. A flat air capacitor with an electric capacity of C1 = 1 pF is connected to the emf source ε = 500 V. Having disconnected the capacitor from the emf source, the distance between the capacitor plates was increased by n = 3 times. Determine the work of external forces to extend the plates.

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