Question

Dry air can support a maximum electric field strength of about 10 x 10^6 V/m. The field creates enough ionization in the air to make the air a conductor. what is the the voltage between two parallel conducting separated by 2.5 cm of dry air

Answer 1

The voltage

$$V=Ed\\ =10*10^6*0.025=250000\:\rm V=250\: kV$$