Why is it said that electrons are negatively charged

 The separation of electric charges into positive and negative still sounds much of a brain box to some curious new physicist, especially in the field of electrical and electronics engineering. But the interesting fact about this is that it was all because of Benjamin franklin's arbitrary decision.

Are you actually a curious type? Do you want to know they full fact behind the ideas that :

1. Electrons possesses a negative charge, while protons are positively charged.
2. Like charges repel while unlike charges attract

This post will explain all of the in depth concept of electric charges using the theory of static electricity. 

Why do knowing these facts matter:   Real scientists and inventors who make a difference don't only limit themselves with implicit explanations, but they move further to know more on the underlying concept of scientific theories. Of cause there is no big deal about just seeing things as everyone does, but to be an inventor, you'll have to be curious enough to fully grasp the root cause of how things actually works, not just how to make things.

What are charges anyway 

To understand the concept of electric charges, let first revisit the past a bit.

          It was discovered centuries ago that certain types of materials would mysteriously attract one another after being rubbed together. For example: after rubbing a piece of silk against a piece of glass rod, the silk and glass would tend to stick together. Also, when a paraffin wax is rubbed with wool cloth; they are seen to attract each other. Indeed, there was an attractive force that could be demonstrated even when the two materials were apart.

This phenomenon became even more interesting when it was discovered that identical materials, after having been rubbed with their respective cloths, always repelled each other. For example: lets consider two glass rods rubbed with silk and brought together. They are seen to repel each other:

Even the materials used to do the rubbing will also tend to repel each other. For example: Two wool cloths will be seen to repel each other after they were used to rub different paraffin wax. Same goes for two silk cloths used to rub different glass rods.

What could have caused this invisible force of attraction and repulsion?  Whatever change that took place to make these materials attract or repel one another was invisible.

         Some experimenters speculated that invisible ”fluids” were being transferred from one of the material to another during the process of rubbing, and that these ”fluids” were able to effect a physical force over a distance. Charles Dufay was one of the early experimenters who demonstrated that definitely two different  types of changes  took place by rubbing certain pairs of objects together.  This idea that there was more than one type of change manifested in these materials was due to the fact that  two types of forces were produced: attraction and repulsion. The hypothetical fluid transfer became known as a CHARGE.

         

What is the concept of positive and negative charges

 One pioneering researcher, Benjamin Franklin, came to the conclusion that there was only one fluid exchanged between rubbed objects, and that the two different ”charges” were nothing more than either an excess or a deficiency of that one fluid. After experimenting with wax and wool, Franklin suggested that the coarse wool removed some of this invisible fluid from the smooth wax, 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. 

           His postulations reveal that during the rubbing process, the two materials concern must fall into either of the two opposing categories. In other words, one must be in excess while the other must be in deficiency. There was never a time where two materials rubbed against each other both became either in excess or in deficiency. 

          Following Franklin’s speculation of the wool rubbing something off of the wax, the type of charge that was associated with rubbed wax became known as ”NEGATIVE” (because it was supposed to have a deficiency of fluid) while the type of charge associated with the rubbing wool became known as ”POSITIVE” (because it was supposed to have an excess of fluid). Little did he know that his innocent conjecture would cause much confusion for students of electricity in the future!

 

 NOTE: The idea of using negative and positive as the word was simply an arbitrary decision by franklin. Since the word "negative" always refers to lack of something and positive designated to a possession of...  

Why is the word "negative" designated to Electrons and "positive" to protons

        It was discovered much later that this ”fluid” was actually composed of extremely small bits of matter called  ”ELECTRONS ”, so named in honor of the ancient Greek word for amber: another material exhibiting charged properties when rubbed with cloth. Experimentation has since revealed that all objects are composed of extremely small ”building-blocks” known as ATOMS, and that these atoms are in turn composed of smaller components known as particles. The three fundamental particles comprising most atoms are called protons, neutrons and electrons. 

However, electrons have significantly more freedom to move around in an atom than either protons or neutrons. In fact, they can be knocked out of their respective positions (even leaving the atom entirely!). If this happens,  an important imbalance will  occur. Electrons and protons are unique in the fact that they are attracted to one another over a distance. It is this attraction over distance which causes the attraction between rubbed objects, where electrons are moved away from their original atoms to reside around atoms of another object.

            Electrons tend to repel other electrons over a distance, as do protons with other protons. The only reason protons bind together in the nucleus of an atom is because of a much stronger force called the strong nuclear force which has effect only under very short distances. Because of this attraction/repulsion behavior between individual particles, electrons and protons are said to have opposite electric charges. That is, each electron has a negative charge, and each proton a positive charge.

The process of electrons arriving or leaving is exactly what happens when certain combinations of materials are rubbed together: electrons from the atoms of one material are forced by the rubbing to leave their respective atoms and transfer over to the atoms of the other material. In other words, electrons comprise the ”fluid” hypothesized by Benjamin Franklin. The result of an imbalance of this ”fluid” (electrons) between objects is called static electricity. It is called ”static” because the displaced electrons tend to remain stationary after being moved from one insulating material to another. In the case of wax and wool, it was determined through further experimentation that electrons in the wool actually transferred to the atoms in the wax, which is exactly opposite of Franklin’s conjecture! In honor of Franklin’s designation of the wax’s charge being ”negative” and the wool’s charge being ”positive,” electrons are said to have a ”negative” charging influence. Thus, an object whose atoms have received a surplus of electrons is said to be negatively charged, while an object whose atoms are lacking electrons is said to be positively charged, as confusing as these designations may seem. By the time the true nature of electric ”fluid” was discovered, Franklin’s nomenclature of electric charge was too well established to be easily changed, and so it remains to this day.

Why do like charges repel and unlike charges attract

If we take the examples of wax and wool which have been rubbed together, we find that the surplus of electrons in the wax (negative charge) and the deficit of electrons in the wool (positive charge) creates an imbalance of charge between them. This imbalance manifests itself as an attractive force between the two objects:

The imbalance of electrons between the atoms in the wax and the atoms in the wool creates a force between the two materials. With no path for electrons to flow from the wax to the wool, all this force can do is attract the two objects together

Dedicated to the book "Lessons In Electric Circuits, Volume I – DC"

 By Tony R. Kuphaldt