Dry air will support a maximum electric field strength of about 3.0 x 10⁶ V/m. Above that value, the field creates enough ionization in the air to make the air a conductor. This allows a discharge or spark that reduces the field. What, then, is the maximum voltage between two parallel conducting plates separated by 2.5 cm of dry air?

Strategy

We are given the maximum electric field E between the plates and the distance d between them. The equation V_AB = Ed can thus be used to calculate the maximum voltage.