Electromagnetism


 * * electricity = phenomenon involving electric charges
 * **common examples are static electricity and lightening** || The existence of [|electricity], the phenomenon associated with stationary or moving electric charges, has been known since the Greeks discovered that amber, rubbed with fur, attracted light objects such as feathers. Ben Franklin proved the electrical nature of lightning (the famous key experiment) and also established the conventional use of negative and positive types of charges. ||

By the 18th century, physicist Charles Coulomb defined the quantity of electricity later known as a coulomb, and determined the force law between electric charges, known as Coulomb's law. Coulomb's law is similar to the law of gravity in that the electrical force is inversely proportional to the distance of the charges squared, and proportional to the product of the charges. By the end of the 18th century, we had determined that electric charge could be stored in a conducting body if it is insulated from its surroundings. The first of these devices was the Leyden jar. consisted of a glass vial, partly filled with sheets of metal foil, the top of which was closed by a cork pierced with a wire or nail. To charge the jar, the exposed end of the wire is brought in contact with a friction device. ||
 * * Coulomb quantifies amount of charge and discovers force law between charges
 * electrical force is similar to gravity in that it is inverse proportional to the square of the distance between charges
 * charges are assigned positive or negative values
 * **like charges repel, opposites attract** || It was also known that certain materials blocked electric charge, called insulators, such as glass or cork. Other materials transfered electric charge with ease, called conductors, such as metal.

The battery was invented in the 19th century, and electric current and static electricity were shown to be manifestations of the same phenomenon, i.e. current is the motion of electric charge. Once a laboratory curiosity, electricity becomes the focus of industrial concerns when it is shown that electrical power can be transmitted efficiently from place to place and with the invention of the incandescent lamp.
 * * modern atomic theory explains the origin of electric charge to the existence of small negative particles (electrons) and small positive particles (protons)
 * an atom can gain electrons in its outer shells to gain negative charge or
 * lose electrons increasing the strength of the proton charge (positive)
 * while each atomic charge is small, the number of atoms in a typical macroscopic piece of matter is very large
 * **thus, electric power becomes the primary source of energy for civilization** || Modern atomic theory explains this as the ability of atoms to either lose or gain an outer electron and thus exhibit a net positive charge or gain a net negative charge (since the electron is negative). Today we know that the basic quantity of electric charge is the electron, and one coulomb is about 6.24x1018 electrons.

Thomas Edison created the very first edition of the light bulb. Ironically, he was also afraid of the dark. ||