LESSON 1 - ELECTRON THEORY

BOHR'S ATOMIC THEORY

Before we start to teach topics dealing with electron flow in an electrical circuit, we need to
know what an electron actually is. After all, it could be a type of alien being or motor car (".... here I was driving down the highway in my new Electron ..." ), so we need to make sure that all of our students know what electrons are and how they form the very basis of all electrical theory and application.

In 1913, the Danish physicist Niels Bohr managed to explain the spectrum of atomic hydrogen by an extension of Rutherford's description of the atom. In Bohr's model, the negatively charged electrons revolve about the positively charged atomic nucleus because of the attractive electrostatic force according to Coulomb's law.

So where are we leading ? How does this explain how these electrons flow through copper wires and light up our lives ?

The main parts of an atom are protons and neutrons that are grouped together in the nucleus ( centre), and electrons.

Neutrons have no electrical charge. Protons are positively charged particles, therefore the overall charge on the nucleus is positive.

Clear so far ?

Electrons are very small negatively charged particles. The amount of electrical charge on an electron is equal but opposite to the charge on a proton. Electrons are continuously moving in orbits, or shells, around the nucleus. A normal atom contains the same number of protons and electrons. The atom is therefore balanced electrically.

Now for the story you wanted to hear !!

As the electrons in the outer shell of an atom are relatively far away from the restraining influence of the nucleus, it is possible for an atom to gain or lose electrons and become electrically unbalanced.

When this occurs the atom becomes an ion. The process of gaining or losing electrons is known as ionisation.

Each outer shell revolving in orbit around the nucleus, somewhat like a spacecraft, has a different limit to the amount of electrons it can hold, but when a shell is the outermost one, its limit is eight. The number, which is actually in the outer shell, determines whether the substance will be a conductor or insulator. A full or nearly full outer shell produces an insulator, nearly empty produces a conductor.

In the next lesson, we'll discuss various conductors and insulators as well as semi-conductors ( the " things" that drive your Ipod ) and start to investigate how current flows.

-------------------------------------------------------------------------------- We hope you found this informative and helped to explain what electrons actually are before we move on to explain how they flow through the wires and cables that enable us to enjoy the benefits of electric power