A friend just reminded me about a trick I was telling everyone about
in past years but had since forgotten.
The "high-voltagist", most painful "static zaps" occur when you exit your
car during low humidity conditions and then touch the metal car door.
Yow! But you can eliminate them entirely, even if you lack car keys. In
other words, the passengers can do this too.
Simply hold onto the metal car door as you climb out of the car. No zap.
The charge-separation occurs as you sit on the seat, but the voltage stays
low until you separate your backside from the surface of the seat. This
is called Capacitive Voltage Multiplication. (Physics lesson: put two
metal plates within a mm of each other, charge them to 1000V, then reduce
the capacitance by pulling them apart and measure the voltage. The
voltage becomes enormous.) However, if you touch the metal shell of the
car while still seated, THEN climb out of the car while still holding the
metal, your body voltage remains nearly at zero voltage with respect to
ground.
This effect takes a bit more explaining. What happens to the opposite
charge you leave behind? Remember that the region of opposite charge on
the carseat is enclosed within a conductive surface, a Faraday Cage. The
Faraday Ice-pail phenomenon occurs, and the entire outside surface of the
car appears to become charged to the same level as the charge on the car
seat. This occurrs because the charge on the car seat induces opposite
charge on the inner surface of the car's frame, and induces alike charge
on the outside of the car's frame, almost as if the charge on the carseat
had magically migrated to the exterior of the car's frame.
So, if you grab the metal door as you climb from the car, the charge on
your body is cancelled by the opposite charge appearing on the outside of
the car's frame. This still leaves the opposite charge on the car seat,
and leaves an alike charge on the INSIDE of the car's frame. The interior
of the car is like the dielectric of a charged capacitor. If an unwitting
victim climbs into the car, they may receive a shock from the first bit of
metal they touch. For the driver, this is usually the keyhole, and the
driver is grasping the car keys at the time, so this other "static zap"
may rarely be noticed.
(((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))
William J. Beaty SCIENCE HOBBYIST website
billb@eskimo.com http://amasci.com
EE/programmer/sci-exhibits amateur science, hobby projects, sci fair
Seattle, WA 206-789-0775 unusual phenomena, tesla coils, weird sci