1. Find the breakdown voltage of a parallel-plate capacitor, assuming that conducting plates are 50mm apart and the medium between them is air.

2. Find the breakdown voltage if the entire space between the conducting plates is filled with plexiglass, which has a dielectric constant 3 and a dielectric strength 20(kV/mm).

3. If a 10 mm thick plexiglass is inserted between the plates, what is the maximum voltage that can be applied to the plates without a breakdown?