How much of a static charge would you have after shuffling your feet on the carpet, if it arcs 1/4 inch to a doorknob? 1/8 inch? 1/2 inch?
Understood that the humidity of the air would make a difference, what’s the approximate value?
Stimulated partly by this thread in MPSIMS, about a highly dubious report of a static issue.
Dry air has a breakdown voltage of about 3 million volt/meter. So for 1/4" (about 6 mm) the answer is 18000 volts.
Well I have always heard the general rule “24,000 volts per inch.”
The differences in the numbers cited demands some explanation. My 3 million volts/m is for breakdown between flat plates of large extent in dry air. This is an ideal condition that produces the maximum breakdown voltage.
The 10000 volt/inch is a statement of the amount of space to leave between points of different voltage to avoid any chance of arcing in a system that depends upon air for insulation. For example, around the high voltage part of a cathode ray tube circuit.
The 24000 volt/inch number looks like one that does the same thing as above except with a lower safety factor.
My 18000 volt number would be a maximum. The electric field intesity around a sharp point is increased over a that between flat plates so if you point your finger at the door know, breakdown would probably occur at a lower voltage than 18000.
The 40000 volts being bandied about in the other thread isn’t unreasonable. The electrical capacitor of the human body can be charged up to pretty high voltages with a relatively small amount of electricity and will hold that charge if you don’t go near any conductors.