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Re: funny capacitor (EUREKA ?)



Brian Whatcott wrote:

Let me tell you how a person, as it might be an engineer or a
physicist, can use the DC properties of a series
string of capacitors as an illustration of how the charge applied
to these components cannot necessarily be deduced from a knowledge
of the DC volts then applied to the ends.

One prepares a series string of three capacitors large enough
to hold a reasonable charge for a reasonable time.
They could be placed in a black box.
One charges cap1 to plus 10 volts, one charges cap2 to -10 volts.
One checks cap3 is uncharged.
(At DC, the capacitors are holding a charge. This is the fundamental
definition of a capacitor, I suppose, so yes! caps exist at DC.)

Demonstrate that there is zero volts across the end of the caps,
then connecting them to a 10 volt source though a 1 megohm resistor,
note the time for the charging current to fall to 1/e of its
initial value.
Ask if the charge stored on the capacitor string can now be deduced.

(This was something like the example I mentioned some years ago
on the list, during one of the famous capacitor dissention threads).

Possibly you are referring to:
http://physics.usna.edu/physics/faculty/mungan/Scholarship/Capacitors.html
--
Carl E. Mungan, Asst. Prof. of Physics 410-293-6680 (O) -3729 (F)
U.S. Naval Academy, Stop 9C, Annapolis, MD 21402-5026
mungan@usna.edu http://physics.usna.edu/physics/faculty/mungan/