Electrical Engineering ⇒ Topic : Kirchhoffs Current Law as Applied to Parallel Circuits

Kirchhoff's current law or Kirchhoff's second law states that "at any junction of conductors, the algebraic sum of the currents is zero." Consider the point x in Fig. 1 (a). Assume that the currents flowing away from point x, (I₁ and I₂) are positive and current flowing towards x, (/) is negative. Then according to Kirchhoff's current law,

                                                       Figure (1)

                                I - I₁ - I₂ = 0                          ............(1)

For the values of V, R₁ and R₂ given in Fig. 1 (a), we get I₁= 3 A, I₂ = 2 A and I = 5 A. Thus, according to Kirchhoff's current law,

                              I₁ + I₂ = 5 i.e. 3 A+ 2 A= 5 A

As in the series circuits, the total power consumed in a parallel circuit is equal to the sum of power consumed in the individual resistances in the parallel branches.

Referring to Fig. 1 (a), the total power consumed is

                      P = VI₁ + VI₂

                      P = 30 x 3 + 30 x 2 = 150W

Total power consumed can also be calculated as

                      P = VI= 30 x 5 = 150 W.