Real/Average Power

Real or average power:  "P" can be defined in two ways: as the real part of the complex power or as the simple average of the instantaneous power. The  second definition is more general because with it we can define the instantaneous power for any signal waveform, not just for sinusoids. Average Power is a continuously varying ne with time, the average must be obtained by integration. Averaging over one period T of the sinusoidal function will give the average power.

It is given explicitly in the following expression.

Since the “rms” voltage and current are given by:

The average power can now be expressed as:

In reality, average power is more convenient to measure. In fact, the wattmeter, the instrument for measuring power, responds to the average power. It is known as the average over time of a modulated signal. The average power (often simply called "power" when the context makes it clear) is the average amount of work done or energy transferred per unit time.


By: Kirk Macaraeg