basic capacitor questions

[Kyle Jarger]

scott   64k at geocities.com wrote:

> 3. Shorting the ends of a cap will drain any leftover charge, right?

Oh, yeah, I forgot that there is a technicality here.
Some capacitors have a "memory" effect, so that you can never drain 
all the charge.  So, for example, you could have it shorted for a long 
time, and then when you leave it open circuit for a while, a voltage 
will develop across the cap "out of nowhere". (Actually, the energy 
was stored in the dielectric)

I know this occurs on high voltage (5 KV) film caps we use at the day job, 
I don't know off the top of my head whether it occurs in the types of 
caps used in low voltage circuits.

Regards,
Kyle Jarger
jkjelec at tiac.net
JKJ Electronics
Visit our MIDI/CV website http://www.tiac.net/users/jkjelec