Electrical engineers find it convenient to model impedance with complex numbers. In a parallel AC circuit with two impedances 21 and 22, the equivalent or total impedance in ohms can be determined by using the Z₂ Z2 formula Zeg Find the equivalent impedance Zeg for 21 = 2-i and 21-22 22 = 1 + i arranged in a parallel AC circuit. The equivalent impedance in a parallel AC circuit is Zeq = i.