Current Electricity Flow of Electrons Engineering Tutorials

The Nature of Electricity
The modern theory defines matter as electrical in nature. All matter is made up of extremely small particles called molecules, each of which has the properties of matter of which it is a constituent. The molecules, in turn are made up of atoms, which are the smallest units of several elements. An atom consists of central nucleus of positive charge around which small negatively charged particles, called electrons, revolve in different paths or orbits.

Free Electrons
The electrons which can be easily removed or detached from an atom are called free electrons.
In metals, the atom lie very close together in regular formed crystal lattice. The nearness of one atom to another causes the electron in the outer orbit or valence electrons of each atom to be attracted by the nucleus is relatively weak. As a result, a large number of electrons are free to drift about interatomic space from atom to atom. These are called free electrons. The free electrons can be easily removed by applying a small amount of external energy.

Charge
A body is said to be charged if it has either excess or deficit of electrons from normal due share. If an electron is freed from a neutral atom, the proton predominate and the atom is said to posses a positive electric charge.

Unit
The unit of charge is coulomb and 1 coulomb is equal to charge on 628 by 10 to the power of 16. We say that a body has a positive discharge of ano coulomb, it means that it has a deficit of 628 by to the power of 16 electrons from normal due share.

Electric Potential
It is a measure of the density and sign of the electric charge at a point relative to that at some time. Thus electric potential, like electric charges and electric current is a phenomenon of displaced charges that exist in matter. For example, consider a copper rod of six meters length having the same number of electrons and protons distributed uniformly throughout.
If by some means, such as intercepting the flux in a magnetic field, one billion electrons can be shifted towards one end of the rod, that end will posses positive charge. The two ends of rod will have a different of potential. Work has been done to create this difference of potential energy.

Nucleus
It is the central part of an atom and contains protons and neutrons. A proton is positively charged particle while the neutron has nearly the same mass as proton, but has no charge. Therefore, the nucleus of an atom is positively charged. The sum of protons and neutrons constitute the entire weight of an atom and is called its atomic weight, it is because the particles in the extra nucleus has negligible weight as compared to protons or neutrons.

Extra Nucleus
It is the outer part of an atom and contains electrons only. An electron is a negatively charged particle having negligible mass. The charge on an electron is equal but opposite to that on a proton. Also, the number of electrons is equal to the number of protons in an atom under ordinary conditions. Therefore, an atom is neutral as a whole. The number of electrons or protons in an atom is called its atomic number.