Electron flow notation

Electron current and conventional current are two types of notation we use to mention current flow in circuit. These two notations are opposite to each other. We need a notation to do some calculations like in Kirchhoff’s law. And we consider conventional current as the standard notation of current flow. But actually this notation is scientifically not correct but all the laws are followed with this notation. So before we get into these notations, we need to understand charges.

Charges – Positive and Negative Charges

First of all Franklin assumed an electric charge which moved in the opposite direction that it should actually be doing, so he called this electric charge “negative” which means deficiency of charges and so we can consider “positive” means surplus of electric charges.

After some time, true direction of flow of electrons was discovered and it was noticed that this labels of positive and negative is incorrect scientifically. But by that time the notation of positive and negative was extremely wide spread and so no efforts were made by engineers to change the old notations. As a result of this, we are still using the same notations that were first assumed by Sir Benjamin Franklin. And this notation we use now is conventional current notation or normal current flow. Let’s discuss it in detail.

Conventional Flow Notation:

 Before starting with this, we associate the word “positive” with surplus of charges and “negative” with deficiency of charges. This has been a label since Franklin first assumed it.

Imagine a battery connected across the conductor. In the electrically stressed conductor, electric charges move from positive terminal to negative terminal of battery. Positive terminal has surplus of electric charges and so this charges are attracted towards negative terminal of battery where there is deficiency of charges. This notation is used widely by the engineers and so it is said as conventional flow notation.

Electron flow notation:

As the name itself says, this notation is based on movement of electrons. This notation shows what actually happens inside an electrically stressed conductor. The negative terminal of battery has high density of electrons. This electron travels from negative terminal of battery where density of electrons is high to positive terminal where density of electrons is less and that’s why they get attracted towards positive terminal of battery.

Conventional flow notation vs. Electron flow notation

This figure shows clear path of conventional current and electron current. They are exactly opposite to each other.

Now, we know the truth that electron flow notation is scientifically correct flow notation though we use conventional current flow most of the time. It doesn’t matter which one you are using you can have correct calculations while applying ohm’s law, Kirchhoff’s law and all other equations. Most of the electronic semiconductors are designed on the basis of conventional flow notation. For example take diode; it is like valve which allows current to flow in only one direction. Here if higher potential is applied to positive terminal of diode and lower potential to negative terminal of diode, then diode will allow passing through the current because this arrangement will break the depletion layer of diode.

                  

And if we reverse the connections, diode will not let the current pass through it.

After all this, you will understand what scientifically true doesn’t matter a lot. You need to just stick to one of it, but just remember that the electrons are moving the other direction.