Physical meaning of imaginary component of impedance


#1

Hello friends.
I have come across a stumbling question while reading an article on impedance and its physical importance. We are used to the general notation of impedance as 1-2j or 3+7j, but in practical situations, we are more concerned about the real values and not the imaginary values. Then what is the physical importance of the imaginary value in impedance expression?


#2

Hello,
In simple terms, the real part is the magnitude and the imaginary part is the phase shift between voltage and current. In other words, the real part represents the dissipated power and the imaginary part represents the power stored by the circuit.

If an AC circuit with a capacitor or inductor has an imaginary impedance, then the current through these elements is out of phase with voltage by 90 degrees. Now, the power dissipated by these elements is the V.I (Dot product). Since V and I are perpendicular, the power dissipated is 0. What that means is that imaginary impedance does not dissipate energy outside the circuit.


#3

Hey, thanks for the help. Now, this makes sense.