You've probably experienced the above scenario hundreds of times in your life. By rubbing your slippers on the carpet, you have given your body an electric charge. Charge is one of the properties of all matter. It has a natural tendency to be transferred between unlike materials. By dragging your feet, you increased this natural transfer.
When scientists first began to study this phenomena, they discovered that there were two kinds of charge. Benjamin Franklin (1706-1790) named these two kinds positive and negative. One of the earliest observations made of charged objects was that unlike charges attract, while like charges repel. A positive and a negative will pull each other together. Two positive or two negative charges will push each other away.
Charge has another important property. Electric charge is always conserved. For example, say you have two neutral, or uncharged, objects, and you rub them together. Let's say object #1 gets a positive charge. Object #2 must have transferred some of its positive charge to #1. Object #2 has become negatively charged.
A famous physicist named Robert Millikan discovered a third property of charge. Charge can
only be found in integer multiples of a fundamental "piece" of charge. He called this piece of
charge e. An electron has a charge of -e, while a proton has an opposite, but equal
in magnitude charge, +e. There is no way to get a charge of +2.71e, because there
are no parts of e, although there could be +2e, there could not be +.71e.
Note: Quarks are an exception to this rule, and have charges of +2/3 or -1/3. Some of the particles physicists used to consider fundamental are actually composed of quarks. This is an advanced topic, and will not be covered here in much depth.
We classify materials into four different types, based on their ability to conduct charge. The four types are: insulators, semiconductors, conductors, and superconductors.
|Force = k (a special constant) * first charge * second charge / the square of the distance between them|
|k = 8.9875*109 N*M2/C2|
You may be thinking to yourself, "This formula is great! If I have two particles. What happens if I have three or more charges?" The answer to your question is The principle of superposition. This law states that if you have three charges, 1, 2, and 3, the charge exerted on charge 1 by the combination of charges 2 and 3 is the vector sum of the force of charge 2 on 1 and the force of 3 on 1. This holds for particle groups of 3, 4, 5, etc.