Click here to register for summer batches of robotics. Click here for details of courses.
- Basic Concepts of Electrostatics
- How does electricity work?
- Faraday’s Laws of Electromagnetic Induction
- Ideal & Practical Voltage Sources
- Internal Resistance of Electric Source
- Ohm’s Law and Concept of AC & DC
- What is Peak, R.M.S. & Average Value of ac voltage and current
- Kirchhoff’s Current Law (KCL)
- Kirchhoff’s Voltage Law (KVL)
- Concept of Electric Power
The KCL is the best tool to analyse the electrical and even electronic circuits. If you learn KCL properly, you will be able to read all the branches in a circuit like we read a book with all pages in it…! So don’t ignore this topic. It is one of the most important topic in fundamentals of electricity and electronics.
Contents
show
Definition
In Kirchhoff’s Current Law, the algebraic addition of all currents in a closed circuit is always equal to zero. It gives us the idea of sign convention of currents in a circuit.
Definition of Node
The node is a point in the circuit to which at least 3 or more than 3 wires or branches are connected.
To understand the KCL, we shall study the following circuit. In this circuit, there four resistors R1, R2, R3 and R4 connected in parallel with the battery of 12V. Also there are six nodes i.e. A, B, C, D, E and F, as shown below.The circuit to understand KCL (click to enlarge)
Observe that the potential difference across all the resistors is same i.e. 12V. So we can calculate the current flowing through each resistor as follows:
The current through will be: I2 = 12V/1Ω = 12A
The current through will be: I4 = 12V/2Ω = 6A
The current through will be: I6 = 12V/3Ω = 4A
The current through will be: I7 = 12V/6Ω = 2A
The current through will be: I4 = 12V/2Ω = 6A
The current through will be: I6 = 12V/3Ω = 4A
The current through will be: I7 = 12V/6Ω = 2A
So the total current that must be delivered by the positive (+) terminal of battery will be:
I = I2 + I4 + I5 + I6 = 12A + 6A + 4A + 2A = 24A
So the current coming out of the battery will be I = 24A
This current splits in two parts at node A i.e. I = I1 + I2 = 12A + 12A = 24A
Then the current I1 splits into two parts at node B i.e. I1 = I3 + I4 i.e. 12A = 6A + 6A
Then the current I3 splits into two parts at node C i.e. i.e. I3 + I5 + I6 i.e. 6A = 4A + 2A
So the current coming out of the battery will be I = 24A
This current splits in two parts at node A i.e. I = I1 + I2 = 12A + 12A = 24A
Then the current I1 splits into two parts at node B i.e. I1 = I3 + I4 i.e. 12A = 6A + 6A
Then the current I3 splits into two parts at node C i.e. i.e. I3 + I5 + I6 i.e. 6A = 4A + 2A
Now these currents again meet at nodes D, E and F to complete the circuit. In this way, it is clear that the total current of 24A delivered by the battery is returned back at its negative (-) terminal.
The KCL finds large number of applications to analyse the complicated electrical and electronic circuits. The general equation of Kirchhoff’s Current Law is given by:
Perfect explanation. Thank you so much sir for starting new series.
Please continue with new topics on semiconductor and mesh analysis.
Thanks again!
I understood it all.
Thank you so much for the nice articles on basic electricity and electronics.
Love this website.