Basics of electricity and electronics
The study of electricity began with ancient Greeks. They observed that when an amber was rubbed using a cloth, there created a force that attracted the cloth to the amber. And they observed that when two pieces of amber were rubbed using two cloths, there created a force that repelled the cloths. These forces were called 'electric' which means 'amber' in Greek. But they weren't able to explain the electric force.
Electricity is not one person's invention. It is not discovered all at once. William Gilbert, Otto von Guericke, Charles Francois, Stephen Gray, Benjamin Franklin, Henry Cavendish and Galvani are some famous inventors in the field of electricity. Benjamin Franklin is famous of his kite-flying experiments of inventing electricity.
Though the Greeks were not able to explain the electric force, the later scientists were able to explain it after the development of the atomic theory of matter; which says that, "Matter is composed of discrete units called atoms" and that atoms are composed of negatively charged particles (electrons) orbiting around the positively charged particles (protons) and particles of no charge (neutrons).
If the number of electrons increase, then the atom becomes negatively charged and if the number of electrons decrease, then the atom becomes positively charged. The charged atoms are called ions.
Unlike charges attract each other, while like charges repel each other.
Electron - Electron is a negatively charged particle having a least mass.
Electric current - Electric current is flow of free electrons. (=charge/time)
Substances that allow free movements of electrons due to their atomic structure are called conductors.(eg: silver, copper, aluminium, etc.) And the substances that have very few free electrons are called the insulators.(eg: rubber, dry wood, glass, etc.)
*Electronics deals with the flow of electrons through non-metal conductors(semi-conductors) while, electricity deals with the flow of electrons through metal conductors.
Electric potential - The capacity of a charged body to do work.
(=work done/charge)
Potential difference - The difference in the potentials of two charged bodies.
Electromotive force - (e.m.f in a device) The measure of the energy in the device which it gives to each coulomb of charge.
*Thus potential difference causes current to flow while an e.m.f maintains the potential difference.
*It is referred the potential difference across the cell as a voltage rise and the potential difference across the resistor as a voltage drop.
Electrochemical reactions - Chemical reactions that produce electrons.
Resistance - The opposition offered by a substance to the flow of electric current which is measured in Ohms.
Ohm's Law - The ratio of potential difference between the ends of a conductor, to the current flowing between them is constant, and is called the resistance. (=voltage/current)
Resistivity - The electrical property of a material that determines the resistance of a piece of a given dimension.(=resistance*area/length)
Electric power - The rate at which work is done in an electric circuit.
(=work done/time)
Electrical energy - The total work done in an electric circuit. (=electric power*time)
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