Understanding Electrical Principles - Kirchoff's Law

Understanding Electrical Principles - Kirchoff's Law, continuation from Ohm's Law Blog

Kirchoff's Law

If you were to Google this, you'd  find the full explanation (and formulae)---quite a mouthful! Fortunately, this blog sticks to what applies here. To explain Kirchoff's Law, I'll separate it into the two different parts--- one applies to voltage and the other to current.

Kirchoff's Voltage Law

Kirchhoff's Voltage Law states that the sum of the voltages applied in a given circuit are equal to the sum of the voltage drops across the various components in a said circuit. The diagram below is an example of a simple lighting circuit with voltage drops specified.   

Here is a simple lighting circuit that illustrates Kirchoff's Voltage Law. Note that the sum of the voltages across each of the lights is the same as the total voltage applied to them.

Kirchhoff's Current Law

Kirchhoff's Current Law states that the current entering a junction in a circuit is equal to the current leaving said junction. The next figure is an example of a different kind of lighting circuit with current flow specified. (Note that this is a different kind of circuit than the last one above -- more on that briefly.)

Recall from your junior high school physical science class when you learned that energy can neither be created nor destroyed.This is called the conservation of energy. Kirchhoff's Law helps us to apply the conservation of energy to basic electronic circuits.

In the example I gave above for the 60watt bulb, it should be clear that the power the filament consumed was divided between light and heat--none was destroyed.

Understanding Ohm's Law and Kirchhoff's Law are paramount in grasping the basics of automotive electronics. Learn them and don't forget them!