At 14:46 03/13/99 -0500, Wagner Lipnharski wrote:
>just a silly thing for laughing:

maybe, but in case you take it seriously, they do have answers...

>if Volts = Resistance Current,
>what is the voltage in a charged perfect capacitor,
>where the resistance between the plates is infinite,
>with zero current flowing between them?
>... hmmm, how much is Infinite Zero?

1) this formula of course applies only where there is =only= resistance
involved (ie. other contributors like capacity negligible). in an ideal
capacitor, the formula is

v = Q / C

(why would you apply the formula for an ideal =resistor= to an ideal
=capacitor=? don't confuse people here... somebody might take you seriously :)

2) "infinite" is not a number and neither a reality. what you actually do
have is a very high value for the resistance and a very low value for the
current. (how long do =your= capacitors hold a charge? mine discharge in
times a whole lot smaller than "infinity." :)

>so, the charged electrons matter in this capacitor?

of course, that's Q [As], the charge in the cap.

>Can we say a capacitor does not hold "Voltage", but
>"charged potential capacity to creates current"?

that's exactly what "voltage" is, i guess.


>If Resistance is  Voltage / Current,
>a simple wire connected to nothing, flowing zero
>Amperes, will has zero volts on its ends. So, what
>is its resistance?
>
>Zero / Zero = Zero?  It can be an isolant!!! and
>will has a zero resitance in this situation???

as long as there is no voltage and no current, the resistance is not
defined (and neither known). this follows from both the mathematical
approach (division through 0 is not defined) and the physical approach
(resistance =is= defined as the relationship between the voltage and the
current, and without any of them there is no way to determine the resistance).

we often talk about resistance (and other quantities of parts) in a pretty
abstract way, without being aware of it. for example, when you say "this
resistor has 5k1," what you actually mean is "when i send a dc current of 1
mA through this resistor, i can measure a voltage of 5V1 at its terminals."
which doesn't necessarily mean that the equivalent is true for 1fA or 1kA.
in these cases, the resistance of the same part might well be a whole lot
different, because it creates a different voltage than the one derived from
the resistance at 1mA. so the resistance of our "5k1 resistor part" at 0 A
is actually not only not defined but also not known. and in some real cases
this fact that the values are only valid over a certain range may create
problems -- always then when you get out of the linear range of your parts
(eg. over voltage for resistors or high frequencies for caps, to cite two
common cases).

ge