Kirchoff's Laws

Two number's of Kirchoff's laws are there and used for:
(1) Calculating Equivalent resistance of complicated circuit.
(2) Calculating current flowing in various loops and conductors used in the circuit

Laws are as follows:

1. Kirchoff's Current Law (KCL) 

This law states that in any electrical circuit/network, the algebraic sum of currents meeting at a point is zero. 

              We can also say that total current entering a point is equal to the total current leaving that point i.e. the net sum of both leaving and entering currents at the point is zero.

                           Consider a group of conductors meeting at one point (Node), Let Currents I1, I2, and I3 entering the node while Current I5 and I4 leaving out the node as shown below:

                        

Assume Incoming or Entering currents to be positive while outgoing or leaving currents to be negative then according to KCL law

       I1 + I2 +I3 +(-I4 + -I5) = 0

or    I1 + I2 + I3 - I4 - I5 = 0

or    I1 + I2 + I3 = I4 + I5

i.e.     Incoming currents = Outgoing Currents  

2. Kirchoff's Voltage Law (KVL)

This law states that The algebraic sum of the products of currents and resistances in each of nodes in any closed loop in a network plus the algebraic sum of the e.m.fs. in that path is zero.

i.e.                  ƩIR + Ʃe.m.f. = 0

In other words we can say that if we start from a point and go through whole loop then return back to same point from where we started we must be at the same potential.