2. Impedance and Admittance

 IMPEDANCE - is a complex quantity having the dimensions of ohms Ω  and symbolized by Z.

In other words, Impedance's in AC behave analogously to resistances in DC circuits: they add in series, and they diminish in parallel. A revised version of Ohm's Law, based on impedance rather than resistance, looks like this:

• REVIEW:

It is important to remember that before series-parallel reduction (simplification) can begin, you must determine the impedance (Z) of every resistor, inductor, and capacitor. That way, all component values will be expressed in common terms (Z) instead of an incompatible mix of resistance (R), inductance (L), and capacitance (C).

ADMITTANCE - is an expression of the ease with which alternating current ( AC) flows through a complex circuit or system and symbolized by Y =(Siemens - s).

• REVIEW:

Like impedance, admittance is a complex quantity rather than scalar. Again, we see a certain logic to the naming of this new term: while impedance is a measure of how much alternating current is impeded in a circuit, admittance is a measure of how much current is admitted.