AC Circuits
A resistor obviously limits the current in a circuit. But, as we just saw, a capacitor and an inductor also limit the current in an AC circuit. However, the reactances do not just add together. Using the fundamental relations and the calculus, we come up with the concept of impedance, Z: V = IZ where Z takes into account all three reactances: XR=R, XL=?L and XC= 1/?C:
Z = [R2 + (wL - 1/wC)2]1/2.
Power, however, is still: Pavg = I2R (not P=I2Z).