On Dec 24, 8:15*pm, Roger wrote:
Roy Lewallen wrote:
Roger wrote:

Thanks for the example of P = V(t) * I(t).

I think the example illustrates why the instantaneous power equation P
= V * I that Keith was referencing is not appropriate at all points on
the line. *If I understood Keith correctly, he would have calculated
200 watts input for your example (100 volts at 2 amps).

Huh? I calculated 160 watts using P = V(t) * I(t). Why do you think
Keith would have calculated 200 from the same equation? I have no doubt
that his math skills exceed mine, and I used nothing more than complex
arithmetic and high school trig.

Why is it the same equation? *I understand your P = V(t) * I(t) to be V
and I as functions of time, but Keith to be using what ever he reads
from his voltmeter and ammeter.

My apologies for being not being completely clear.

My voltmeter is always one that is appropriate for the situation.
A d'Arsonval movement would work at sufficiently low frequencies
but for the ones under discussion an oscilloscope would probably
be more appropriate. It would be a voltmeter that would be able
to measure the actual voltage at a point on the line at a particular
time. I.e. V(x,t)

Again, apologies.

...Keith