|MadSci Network: Physics|
Dear James: You ask about making low voltage lightning in the laboratory if you make a stream of ionized air. The answer to your question depends a lot upon what you mean by "lightning". Normally lightning refers to the natural phenomenon during a thunderstorm; in that case extremely high voltages are generated between the clouds and the earth, and when the voltage is high enough (an electric field of 33,000 volts/centimeter breaks down the air into a lightnint bolt) then lightning occurs. This lightning is like an arc discharge, which means the currents are very very high, and the light is very bright, and in a very short time the huge current drains away all the voltage and the lightning is over. So regular lightning is a catastrophic phenomenon which starts suddenly when the air breaks down, and is over almost immediately because the charge is drained away by the very large currents. If you have a path of ionized air already there, then it is possible if you apply the voltage very quickly so that the voltage builds up very high before the the current has time to drain it away there can be a breakdown of the air and a lightning bolt might be created at perhaps a somewhat lower voltage. If by "lightning" you really mean a "spark", you could make a spark at very low voltage compared to real lightning (which is millions of volts!)by having ions in the air already; however the spark would go out very quickly because the high current in the spark drains away the voltage just like lightning and it is over very quickly. It would be really tiny compared to real lightning. So the answer depends a lot on what you mean by your question! R. Bersin
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