Electrical Engineering ⇒ Topic : Equivalent Impedance Method

Equivalent Impedance Method

In this method, we find the equivalent or total impedance of the parallel circuit. The line current is equal to the applied voltage divided by the equivalent impedance. Consider several impedances connected in parallel as shown in Fig. (a)

                                                      figure (a)

Note that relation (i) compares with that for parallel resistors but with one important difference.Here each impedance is in complex form and takes care of magnitude as well as impedance angle.Therefore, all algebraic operations (e.g. addition, division, subtraction etc.) must be in complex form. No attempt should be made to carry out these operations airthmetically.

Special case. If only two impedances are in parallel, then the total or equivalent impedance is given by ;

The reader may note that finding the equivalent impedance in complex form involves lengthy calculations. Such an approach to solve parallel a.c. circuits is not recommended particularly when there are more than two branches in the circuit.