Q:

What is the dielectric breakdown strength of air?

A:

Quick Answer

The breakdown of air is roughly three kV/mm; however, the precise dielectric strength of air depends on the conditions of the air involved. If, for instance, the air pressure is higher, the air's dielectric strength will also be higher.

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Full Answer

Dielectric breakdown in the air occurs following an accumulation of energy up to the level of three kV/mm. An example occurs in conditions leading up to a lightening storm. Electrons from the ground, which act as mobile charge carriers, try to reach the positively charged ions in a cloud. The air in the cloud initially acts as an insulator, preventing electrons from entering. A section of the cloud slowly moves from an insulated state to a state of conduction as electrons begin to interact with the air in the cloud. The electrical fields in the cloud now have the potential to create a conducting path straight to the ground. When the electrons and ions move toward each other, they collide, creating sparks on a non-observable scale. These little collisions charge a section of air in the cloud, enabling more dramatic action. Once this energy has increased to a certain threshold, a lightning bolt is produced. This occurs when the electric field exceeds the dielectric strength of the air.

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