Inductors in AC The following diagram shows a circuit with an AC power source, an inductor and a resistor with connections to the channels of an oscilloscope indicated. Channel 1 Channel 2 R Given an AC current I(t) = I cos(wt) and source voltage V(t) = V cos(wt + $) and that V(t) = VI(t) + VR(t), the following relationship is found for the circuit above: V cos(wt + $) = -IwL sin(wt) + IR cos(wt) It can be shown that the following relationship holds for the amplitudes of each term in the above: V2 = (WLD)2 + (IR)2