Supposed there is a black box connect to an AC circuit. Inside the black box, there are either a resistor connected with a capacitor or a resistor connected with a inductor. They can be connected either in series or in parallel. The total impedance and phase shift of the black box at 2 different frequency are given. How can I figure out what components are inside the black box and how are they connected? I know I can figure out if there is a capacitor or an inductor inside by comparing the change of the total impedance to the frequency change. If the total impedance increase as the frequency increase, there is an inductor inside. Otherwise, there is a capacitor inside. However, how can I figure out if they are connected in series or parallel? Should I compare the change of the phase shift to figure it out?