# AC power: what's the average (real) power, and how it’s related to complex power?

#### JohnTZ

Joined Mar 30, 2015
4
Could anyone please explain and help me understanding following question?

what's the average and rms values for a sinusoidal signal? what's the average (real) power, and how it’s related to complex power? Also, What is the difference between average and rms voltage? and Which of the three voltages (rms, Average, peak-to peak voltage) is best to describe an AC signal?why? and what happens to the Pav when it go above and below the resonant frequency? Please explain why.

Thank you for help.

#### Papabravo

Joined Feb 24, 2006
15,730
The average value of a sinewave over a period is zero
The RMS value is 0.707 times the peak value. It is found by squaring the sinewave, averaging the squared sinewave over 1 period, and finally taking the square root.
It so happens that for a resistor, the power dissipated in that resistor is Irms squared times R. It is the same power dissipated as if Irms was a DC current into the same resistor.
Ac current flows into and out of reactive elements on each cycle and there is no heating or power dissipation in the process, assuming ideal components. Thae actual power in an AC circuit is due to resistance alone.

• JohnTZ and cmartinez