On Jan 12, 4:24*pm, Cecil Moore wrote:
On Jan 12, 3:25 pm, Keith Dysart wrote:

But, of course, V(t) and I(t) are general functions
of time. In particular, the discusion was regarding
pulses.

Pulses can be analyzed as Fourier sinusoidal functions with multiple
frequencies. Point is that you could have saved a month of grief on
this newsgroup if you had initially said your power equation applied
only to real voltage and real current. If you had done that, nobody
would have argued with you.

An earlier post suggested that you "had got it", but these
last two posts leave me wondering.

P(t) = V(t) * I(t)
where V(t) and I(t) are functions describing the actual
measureable voltage and current at a point on the line.

Examples of V(t) would be
V(t) = 10
V(t) = A cos(wt + a)

These functions all yield real results since the voltage
measureable at a point on the line is a real function
of time.

When the latter example is written in complex exponential
form it becomes
V(t) = Re[A*e^j(wt+a)]

Re[] is not there because there is some imaginary part
to be ignored, but because this is how one writes the
function for V(t) in this notation.

Thus Re[V(t)] is non-sensical since the Re[] is already
in the expression describing the function.

My apologies for not detecting this subtle bit of
misleading thinking when I wrote my earlier reply.

...Keith