21. A droplet of oil with a radius of 1 μm, carrying a charge of two electrons, is in equilibrium in the field of a horizontally flat capacitor when a voltage of 820 V is applied to it. The distance between the plates is 8 mm. The density of the oil is 0.8 g / cm3. What is the charge of an electron?

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