Vocabulary:
Coulomb: The unit of electric charge. One electron has a charge of -1.6x10-19 C. One coulomb is a very large amount of charge when isolated (enough particles of one charge kept away from all particles of the other charge to add to a whole coulomb).
Volt: The unit of electric potential. One Joule per Coulomb.
Electric Potential: The amount of energy possessed by a unit of charge at a particular point in an electric field. The units are therefore Joules per Coulomb. The derived unit equivalent to Joules per Coulomb is the Volt. Electric Potential is a property of the electric field, whether any charged particle is in the field or not.
Electric Potential Energy: The amount of energy possessed by a charged particle or object placed at a particular place in an electric field. Like any form of energy, electric potential energy is measured in Joules. Electric Potential Energy is a property of the particle in the field, not of the field itself.
Work in an electric field: To move a charge from one point in an electric field requires work. The work does not depend on the amount of distance, rather it depends on the amount of charge moved and the change in potential through which it is moved.
Charge: Charge is a fundamental property of nature. It can be traced to quarks and electrons. Electrons carry a charge of -1 (-1.6e-19C). Protons are a combination of quarks with charges that sum to +1 (+1.6e-19C). The proton is two Up quarks and one Down quark. The up quark has a positive charge with a magnitude equal to two-thirds that of an electron. The down quark has a negative charge equal to one-third that of the electron. Do the math to compare the magnitude of a proton's charge to the magnitude of an electron's charge. Neutrons are composed of two down quarks and one up quark.
Ordinary objects have nearly equal numbers of protons and electrons and are therefore electrically neutral. Any object with more of one than the other will carry a static electric charge.
An electrically charged object is surrounded by an electric field. A charge placed on a point or symmetrically around a point creates an electric field that diminishes in intensity as the inverse of the square of the distance from the center of charge. The intensity of an electric field at any point in space is an expression of the amount of force that the field exerts against a unit of charge at that point in space. The units of field intensity are therefore Newtons per Coulomb.
The dual nature of electric charge was characterized by Benjamin Franklin who labeled one type of charge positive and the other negative. Franklin's experiments showed that the charge acquired by a piece of amber when rubbed against animal fur was different from the charge acquired by glass when rubbed against silk. Franklin called the charge of the piece of amber "negative" and the charge of the glass "positive".
Oppositely charged objects exert an attractive force on one another and like charged objects a repulsive force.
Coulomb's Law determines the magnitude of the force as equal to the product of Coulomb's constant (k) and the magnitudes of the two charges divided by the square of the distance between them.
Coulomb's Law
