The following is a review of important conclusions that can be derived
from the discussion and examples of the previous sections. The list is
not all-inclusive, but it does emphasize some of the conclusions that
should be carried forward in the future analysis of ac systems.
For parallel ac networks with reactive elements:
- The total admittance (impedance) will be frequency
- The impedance of any one element can be less than the total
impedance (recall that for dc circuits the total resistance must
always be less than the smallest parallel resistor).
- The inductive and capacitive susceptances are in direct
opposition on an admittance diagram.
- Depending on the frequency applied, the same network can be
either predominantly inductive or predominantly capacitive.
- At lower frequencies the inductive elements will usually have
the most impact on the total impedance, while at high
frequencies the capacitive elements will usually have the most
- The magnitude of the current through any one branch can be
greater than the source current.
- The magnitude of the current through an element, compared
to the other elements of the network, is directly related to the
magnitude of its impedance; that is, the smaller the impedance
of an element, the larger the magnitude of the current through
- The current through a coil is always in direct opposition with
the current through a capacitor on a phasor diagram.
- The applied voltage is always in phase with the current
through the resistive elements, leads the voltage across all the
inductive elements by $90^\circ$, and lags the current through all
capacitive elements by $90^\circ$.
- The smaller the resistive element of a network compared to the
net reactive susceptance, the closer the power factor is to