I frequently see ads selling stun guns that claim unbelievably high output voltages, even as high as two million volts. This is physically impossible.
The spark gaps on stun guns serve two purposes: first, to intimidate a potential attacker, and second, to limit the output voltage to a level that won’t destroy the generating electronics. The spark gaps are typically 1.5 to 2 inches long. The dielectric breakdown voltage of air is about three million volts per meter. One meter is 39.37 inches. That means for one million volts to exist between two points, there would have to be at least 13.12 inches between them. A two-inch gap would limit the voltage to about 152,000 volts.
It is not the voltage that shocks, but the current. You can touch the top of a 100,000 volt Van De Graaff generator, causing your hair to stand on end while suffering no harm or pain. Stepping the voltage up too high can actually reduce your ability to shock someone, since the increase in voltage reduces the available current.
I think the best way to compare the shock power of a stun gun is to hear how loud the spark is, not just how long the spark is. The volume of the “snap” sound is dependent on the actual current flow as well as the spark length. A larger gap would allow someone to get more of their attacker’s flesh between the electrodes, but probably 10,000 volts would be more than adequate to pass current through the attacker’s clothes and cause a shock.
Professional stun gun manufacturers pay attention to the frequency of the pulses in order to mimic the frequency of the pulses in the motor nerves, thus intensely stimulating all the muscles between the electrodes. That stimulation causes temporary paralysis.
So, if you see an ad for a stun gun that claims to produce more than 200,000 volts, don’t believe it.
This entry was submitted by Andrew Morris and edited by Rob Spiegel.
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