lee wrote:
On Thu, Nov 27, 2008 at 10:37:26PM -0500, Napoleon wrote:
lee wrote:
But how do know that there is voltage when you cannot measure it or
otherwise make evident that there is? As far as I understand it, you
cannot do that without current flowing. You can do it for water
pressure without water flowing, but I don't see how you could do it
for voltage without flow.
Actually, you can't do it for water without some water flowing,
either.
Ok, but once the measuring device shows the pressure, the water stops
flowing. Hm, ok, maybe you can design a voltmeter that shows the
voltage and stops the flow of current ...
The same is true for voltage. You can't *measure* it without some
current flowing. But just because you aren't measuring it does not mean
the voltage does not exist. Just as the water pressure still exists,
even when you are not measuring it.
It's likely that voltage and water pressure exist even when you don't
measure them, but without measuring them (or otherwise observing their
effects), you don't know that they do. Not oberserving something
doesn't mean that it still exists.
It also does not mean it does not exist.
The question is immaterial. Whether you know or not is not related to
the presence (or absence) of voltage.
But measuring/observing is?
Measuring/observing has nothing to do as to whether something exists in
the macro world - only in quantum physics (which we are not discussing
here).
Right now I don't have a thermometer, so I can't measure the outside
temperature. However, I am confident it exists!
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