On Dec 24, 10:49*am, Cecil Moore wrote:
Keith Dysart wrote:
Are you really saying that if I measure the instantaneous
voltage and the instantaneous current then I can NOT multiply
them together to obtain the instantaneous power?

It certainly works some of the time.

If I can not do it all the time, when can I do it?

Actually, "multiply" is ambiguous. You need to take
the *dot product* of the voltage and current to
obtain power.

Since the discussion concerns real numbers and not
vectors, "multiply" is exactly correct.

But you haven't answered the hard part of the question.
When does P(x,t) not equal V(x,t) * I(x,t)?

...Keith