Paschen's Law

Paschen's Law, named after Friedrich Paschen, was first stated in 1889. He studied the breakdown voltage of gas between parallel plates as a function of pressure and gap distance. The voltage necessary to arc across the gap decreased up to a point as the pressure was reduced. It then increased, gradually exceeding its original value. He also found that for normal pressure the voltage needed to cause an arc reduced with the gap size, but only up to a point. As the gap was reduced further, the required voltage began to rise and again, exceeded its original value.