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.
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