What is KVL (Kirchhoff’s Voltage Law)

In the last lesson, we had a discussion on KCL and now we are going to understand what is KVL (Kirchhoff’s voltage law) and how to apply KVL.             

So let’s move on to the statement of KVL, “The algebraic sum of all the voltages in any closed loop is zero”. So when you calculate the algebraic sum of all the voltages. This means you calculate the sum of all the voltages considering their signs then you will find it is equal to zero in a closed loop. For example, here we have a closed-loop having three elements,

How to apply KVL

Now we know the fact that when current I pass through a resistance R1 there will be a voltage drop and the voltage drop will be equal, to I x R1 (following the ohm’s law)
R1 and R2 are connected in series, therefore the same current I will flow through R2 as well and therefore the voltage drop across R2 to will be equal to  I x R2.

So,    V –  IR1 –   IR2  =  0

This is our KVL equation. 

Here we have followed the convention in which we are considering the rise in potential as positive (+) and the drop in potential as negative (-). 

So the convention is the rise in potential will give you the positive sign and a drop in potential will give you the negative sign. 

Now we will move on to the last point and according to this point the KVL is based on the law of conservation of energy KCL was based on the law of conservation of charge but KVL is based on the law of conservation of energy. The voltage is the measure of potential energy difference across the element we know this point and we also know that there is a single unique value of a voltage therefore the energy required to move a unit charge from one point to other is independent of the path chosen you will get the same voltage potential difference between the two points irrespective of the path you have chosen.