Impedance Diagram

Now that an angle is associated with resistance, inductive reactance, and capacitive reactance, each can be placed on a complex plane diagram, as shown in Fig. 1.
Impedance diagram
Fig. 1: Impedance diagram.
For any network, the resistance will always appear on the positive real axis, the inductive reactance on the positive imaginary axis, and the capacitive reactance on the negative imaginary axis. The result is an impedance diagram that can reflect the individual and total impedance levels of an ac network.
We will find in the sections and chapters to follow that networks combining different types of elements will have total impedances that extend from $+90^\circ$ to $-90^\circ$.
If the total impedance has an angle of $0^\circ$ , it is said to be resistive in nature. If it is closer to $+90^\circ$, it is inductive in nature; and if it is closer to $-90^\circ$, it is capacitive in nature.
Of course, for single-element networks the angle associated with the impedance will be the same as that of the resistive or reactive element. It is important to stay aware that impedance, like resistance or reactance, is not a phasor quantity representing a time-varying function with a particular phase shift. It is simply an operating "tool" that is extremely useful in determining the magnitude and angle of quantities in a sinusoidal ac network.
Once the total impedance of a network is determined, its magnitude will define the resulting current level (through Ohm's law), whereas its angle will reveal whether the network is primarily inductive or capacitive or simply resistive.
For any configuration (series, parallel, series-parallel, etc.), the angle associated with the total impedance is the angle by which the applied voltage leads the source current. For inductive networks, $\theta_L$ will be positive, whereas for capacitive networks, $\theta_C$ will be negative.

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