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	ELECTRICITY Definition Science states that certain particles possess a force field or charge. The charge possessed by an electron is negative while the charge possessed by a proton is positive. Electricity is a phenomena resulting from the presence, flow and effect of electric charge arising from the behavior of electrons and protons that is caused by the attraction of particles with opposite charges and the repulsion of particles with the same charge. Early History The first known scientist Thales of Miletus investigated Static Electricity from the attractive properties of rubbed amber in Ionia around 600 bce. He compared it to magnetism and noted that it was similar, but different. Around 1570, the English scientist William Gilbert also studied magnetism and the corresponding attraction of rubbed amber and various rubbed jewels. He modified the Greek and Latin terms for amber to produce the English word "electric" as a noun describing a material that behaved like amber. Modern History Electricity was discovered by Benjamin Franklin in 1752. The electric generator was invented by Michael Faraday in 1831. Thomas Edison's invention of the electric lightbulb in 1879 sparked the demand for electric power that continues to this day, and initiated the need for legislative and regulatory controls on the electric-power-generating industry. Types Electrostatics is the study of charges at rest. When positive or negative charge builds up in fixed positions on objects, certain phenomena can be observed that are collectively referred to as static electricity. The charge can be built up by rubbing certain objects together, such as silk and glass or rubber and fur; the friction between the objects causes electrons to be transferred from one to the other—from a glass rod to a silk cloth or from fur to a rubber rod—with the result that the object that has lost the electrons has a positive charge and the object that has gained them has an equal negative charge. Electrodynamics is the study of charges in motion. The flow or movement of charges is called the electrical curent "I". Electrical current is measured in amperes "A". Electrical charge "Q" is measured in Coulombs. One Ampere "A" equals one unit of charge "Q" per unit of time "t". i.e I = Q/t. In a conductor or a metal wire there is always a large population of free electrons moving about randomly due to thermal energy but on average there is zero net current in the metal wire. Some external work or energy would be required to move a unit of electrical charge from one point to the other against the electrostatic field that is present. The amount of energy per unit charge needed to move a charged particle from a reference point to a designated point in a static electric field is called the voltage "V", also called potential or the electrical potential difference. The free electron is therefore the current carrier in a typical solid conductor. The amount of energy should overcome the resistance "R" to produce the desired current. Units There are three basic systems of units used to measure electrical quantities, the most common being the one in which the ampere is the unit of current, the coulomb is the unit of charge, the volt is the unit of electromotive force, and the ohm is the unit of resistance, reactance, or impedance. The most comonly used equation for predicting and optimizing the performance of electrical circuits is called the Ohm's Law, I = V/R. It states that, the current, I, passing through the conductor between two points (measured in amperes) is directly proportional to the potential difference, V, (i.e. voltage drop measured in volts) across the two points, and inversely proportional to the resistance, R, (measured in Ohms) between them. It is important to remember that the familiar I=V/R is only valid in a few simple circumstances.