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Jeff Wisnia

wrote:
esters are really, really inexpensive.

And not only that, but if you touch one lead to a hot wire and grab
the other lead (of the neon tester) with your fingers, the neon will
show a slight glow. It wont do that on the neutral. And you wont get
a shock doing this. I do it all the time. To be totally honest, I
really never understood why it lights when touched, but it works.

"It woiks" because your body has "free space capacitance"* which can
accumulate a charge, like it does when you scuff your shoes on a carpet,
and will get discharged when you "spark" to ground (or to another
person's capacitance, sharing your charge with them). The value of your
body capacitance varies from about 100 to 300 picofarads, depending on
whether you are skinny or fat.

AC line voltage connected to one side of the the neon tester drives a
minute current (less than a milliamp) in and out of your body's
capacitance, and that current is enough to make the tester's bulb glow.

* The free space capacitance of an object is the sum mutual capacity of
it to all the conducting objects of the universe. (Wow!)

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.