What is conventional current and why is it opposite to electron flow

Many students of physics and electrical engineering are confused by the idea of conventional current. If current is due to the flow of electrons, and direction of flow of electrons is from negative to positive, then what's with this conventional current of a thing, and why is it opposite to electron flow. 

To understand this post fully, I would recommend you first read about the concept of charged particles  in my previous post on why is it said that electrons are negatively charged. It will give you the ground basis on why it was necessary to introduce conventional current notation. 

This post will explain all you need to know about conventional current and why it opposite to electron flow. But first, let make sure we're on the same page by defining what electric current is.

What is electric current

When defining electric current due to current flow in metallic conductors, we would say that electric current is the flow of electrons. But the story sounds different when we consider the particles actually moving in electrolytes, (for e.g when a voltage source is applied to a glass of salt water,  what will happen is that positively charged sodium ions will move toward the negative terminal while negatively charged chloride ions move toward the positive terminal). This tells us one thing, that charged particles, which could be electrons, protons, ions, holes or both electrons and ions is what constitute current flow. 

      Electric current is thus the measure of flow of electric charge (or charges) through a conductor. But what direction do the charges actually flow to in terms of origin and destination?

What is the direction of electric current

 Benjamin Franklin in his experiment with static electricity, discovered that when a wax and a wool tend to attract themselves after they were rubbed together, it entails that bunch of invisible fluids (later discovered to be electrons) were trying to regain it former balance after they were displaced by the action of that rubbing. This invisible fluids will always flow from the region of excess(denoted to be positive) to the region of deficit(denoted to be negative). Expanding further with the wax and wool experiment, when wax and wool were vigorously rubbed together, invisible fluids will forcefully be displaced from one of the material to another. But from which material to which material?  Franklin then suggested that the coarse wool removed some of this invisible fluids from the smooth wax during the process of rubbing, causing an excess of fluid on the wool and a deficiency of fluid on the wax. The resulting disparity in fluid content between the wool and wax would then cause an attractive force, as the fluid tried to regain its former balance between the two materials.

Advancement in scientific research further made it clear that these ”fluid” was actually composed of extremely small bits of matter called electrons, and that they were actually displaced from the wool to the wax not from the wax to the wool as Franklin suggested. So the wax was the actual region of excess (or positive region) and the wool was the actual region of deficit(or negative). In other words, Franklin's suggested region of excess (which was the wool) was clarified to be the region of deficit and his suggested region of deficit(which was the wax) was clarified to be the real region of excess. So Franklin's conjecture of direction of charged particles was the other way round. What a confusion.

Why was a convention needed?

First of all, what is a science convention? A science convention is an international conference, that holds to set up a precise and generally acceptable standards in science parameters and unit of measurement.

By the time the true direction of electron flow was discovered, the nomenclature of ”positive” and ”negative” had already been so well established in the scientific community that no effort was made to change it, although calling electrons ”positive” would make more sense in referring to ”excess” charge. You see, the terms ”positive” and ”negative” are human inventions, and as such have no absolute meaning beyond our own conventions of language and scientific description. Franklin could have just as easily referred to a surplus of charge as ”black” and a deficiency as ”white,” in which case scientists would speak of electrons having a ”white” charge (assuming the same incorrect conjecture of charge position between wax and wool). However, because we tend to associate the word ”positive” with ”surplus” and ”negative” with ”deficiency,” the standard label for electron charge does seem backward. Because of this, many engineers decided to retain the old concept of electricity with ”positive” referring to a surplus of charge, and label charge flow (current) accordingly. This became known as conventional flow notation.

Hope you liked this post and also understands the reason why what they call conventional current exist and why they say it opposite to electron flow. If you have any doubt or question concerning this article, just include it in the comment box below and don't forget to subscribe if you want to be receiving notifications for interesting post like this one.