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,
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.
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