# capacitor basics

Discussion in 'Electronic Basics' started by [email protected], Oct 14, 2005.

1. ### Guest

sir,

I have a dout about capacitor discharge.Can a charged capacitor
discharge by connecting its one terminal and ground without using its
other terminal.

2. ### BobGuest

The only way to reduce the voltage of a so-called charged capacitor is by
providing a conductive path between the two terminals of that capacitor.

Earth, or ground is only conductive to other parts of the earth (and rather
poorly). People sometimes refer to a common point in a circuit as "ground".
A circuit's "common" only has a conductive path to real ground (earth) if
it's connected to ground (earth).

Bob

3. ### Guest

Sir,
If we touch one terminal of the charged capacitor , is current flow
through our body to the ground without any contact with other terminal.

4. ### RobinGuest

Can you pull a cork out of a bottle one-handed?
No you *have* to use the other hand to hold the bottle.

Likewise the capacitor can only push as much current out of one
terminal as it pulls into the other.

5. ### Andrew HolmeGuest

In electrostatics, you can discharge a body by providing a conductive
path to earth (or anywhere else); but a capacitor is two charged bodies
(plates), holding equal and opposite charges, with an electric field
between them. If you connect a conductive path to one plate, only a
very small percentage of the stored charge will re-distribute itself.

6. ### Andy BaxterGuest

Robin said:
yes - you put the corkscrew in, tie it to a long piece of string, and then
whirl it round very-very-fast...

7. ### Andy BaxterGuest

anilmanual said:
Sir,

You now have a scientific hypothesis on your hands. Namely that you can
discharge a capacitor by touching only one of its terminals to the ground.
The thing to do with scientific hypotheses is to test them, so think of a
way to do so and try it yourself.

8. ### Kitchen ManGuest

Sir, "current flow" is a misuse of terms, and circuits are circular.

9. ### Rich GriseGuest

Yabbut, that doesn't work with electrons. (Or, if you're a college boy,
raised on "conventional current", the holes. ;-P )

Good Luck!
Rich

10. ### Jasen BettsGuest

not unless the other terminal is connected to ground (or to something that
connected to ground etc...)

except, some capacitors leak charge but that is a slow discharge process.

Bye.
Jasen

11. ### Jasen BettsGuest

If nothing is touching the other terminal no current will flow through the
one you touch.

Bye.
Jasen

12. ### Guest

Sir,
What is situation in case of lightning .ie lot of electrons are going
to ground...could u pls tell me the actual process of lightning ....

13. ### John PopelishGuest

In that case, you and the lightning are inside the capacitor, made up
of the ground as one plate and the cloud as the other plate, with the
air between being the dielectric.

14. ### Bill BowdenGuest

The only way to reduce the voltage of a so-called charged capacitor is by
There is a way to reduce the capacitor voltage without a conductive
path. You can add more dielectric, which will increase the capacity,
and reduce the voltage.

-Bill

15. ### Michael A. TerrellGuest

You forgot to mention that the capacitor is over its rated voltage
when it arcs over. ;-)

16. ### John PopelishGuest

Golly! So it is.

17. ### Jasen BettsGuest

That'll increase the voltage unless the dielectric is a gas and the plates
aren't moving apart to accomodate the extra dielectric.

to reduce the voltage move the plates closer together.

18. ### Tim WilliamsGuest

Eh? He means increasing the effective area of the plates. Not increasing
thickness.

Tim

19. ### JamieGuest

actually, i think it's the other way around but then again, i could be
wrong
i think they actually travel from the ground up and when the path
is complete you then get an ionized stream which acts like a short
circuit that gives you that nice little light show ect..

20. ### RobinGuest

No, as originally stated, the voltage will *decrease* with "more
dielectric".

This is because the dielectric is "stretched" and *that* absorbs energy
hence the voltage must drop a little because energy is conserved. See
Feynman's Lectures on Physics volume 2 chapter 10 section 3.

Also see chapter 9 for fascinating (non technical) description of
lightning.

Cheers
Robin

Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Continue to site