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Air Breakdown Voltage

April 25th Fact-of-the-Day

Air is a good insulator at low values of electric field strength, because electrons attach to atoms of oxygen faster than they are knocked loose by collisions. However, if the electric field strength in sea level air reaches approximately three million volts-per-meter the reverse becomes true and air suddenly becomes a conductor (breakdown occurs at a lower voltages at higher elevations). The electric field strength in any given volume of air between charged electrodes is determined not only by the voltage applied to electrodes, but also by electrode shape. For example, the electric field strength in air directly between two spaced, electrically-charged needle point conductors is much higher than electric field strength between two parallel plate conductors with the same spacing and voltage applied. Because of that, it is important to avoid sharp conductor points wherever it is important to avoid electrical discharge through air (in power amplifiers, antenna tuners, and antennas, for example). ©2005 Martek International All rights reserved.


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