Practical Electronics for Inventors, Fourth Edition, 4th Edition

2.28 Power in AC Circuits (Apparent Power, Real Power, Reactive Power)

In a complex circuit containing resistors, inductors, and capacitors, how do you determine what kind of power is being used? The best place to start is with the generalized power law P = I_RMSV_RMS. However, for now, let's replace P with VA, and call VA the apparent power:

VA = IRMSVRMS

(2.74) Apparent power

In light of our RL series circuit in Fig. 2.167, we find the apparent power to be:

VA = I_RMSV_RMS = (0.107A)(12 V) = 1.284 VA

The apparent power VA is no different from the power we calculate using the generalized ac power expression. The reason for using VA instead of P is simply a convention used to help distinguish the fact that the calculated power isn't purely ...