Impedance is the resultant of phasor addition of R and X_L. The symbol for impedance is Z. Impedance is the total opposition to the flow of current and is expressed in ohms. Equation (8-10) is the mathematical representation of the impedance in an RL circuit.

Example: If a 100 resistor and a 60 X_L are in series with a 115V applied voltage (Figure 6), what is the circuit impedance?

Figure 6 Simple R-L Circuit

Solution:

Impedance in R-C Circuits

In a capacitive circuit, as in an inductive circuit, impedance is the resultant of phasor addition of R and X_C. Equation (8-11) is the mathematical representation for impedance in an R-C circuit.

Example: A 50 52 X_c and a 60 52 resistance are in series across a 110V source (Figure 7). Calculate the impedance.

Figure 7 Simple R-C Circuit

Solution: