| MadSci Network: Physics |
The breakdown voltage is highly dependant upon the shape of the electrodes.
For flat electrodes, the "rule of thumb" is 30KV/cm, which gives 3,000v for a 1mm gap.
If the electrodes are not flat (sharp needles, for example), the voltage will be far lower. The breakdown
voltage also is changed by air pressure, dust, illumination, and
electrode materials.
For some more information, see
High-voltage experimenter's Handbook, under Spark Gaps. The Paschen
formula gives 4.4KV for 0.1cm electrode spacing.
Also see Graph of breakdown voltage versus pressure
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