Electric charge

**Electric charge** is a basic property of electrons, protons and other subatomic particles. Electrons are negatively charged while protons are positively charged. Two or more particles with unlike charges attract each other and one with same type of charges repel each other. This makes electrons and protons stick together to form atoms. Charges are also conserved, that is intial charge on any body (bodies) is equal to final charges on them. These rules (or facts) are called the _Law of Charges_. The concept of electric charge and its behavior was first explored by Benjamin Franklin in the 18th century. Later Charles-Augustin de Coulomb and Robert Mullikan deepened the theories of Charge. The law, discovered by Coulomb,  that describes how strongly charges pull and push on each other is called Coulomb's Law.

Materials with equal numbers of electrons and protons have neutral charge (not 0 charge). If the material have more electrons than proton it gains a negative charge whose strength depends on numbers of electrons present in the body. If there are just enough electrons to match the extra protons, then the two things will not attract each other anymore. When electrons move from an area of high concentration to an area of low concentration, this flow of charge is called an electric current.

When a person shuffles their feet on a carpet and then touches a brass doorknob, they may get an electrical shock. If there are enough extra electrons then the force with which those electrons push each other away may be enough to make some of the electrons jump across a gap between the person and the doorknob. The length of the spark is a measure of voltage or "electrical pressure." The number of electrons that move from one place to another per unit of time measured as amperage or "rate of electron flow."

If a person gets a positive or negative charge, it may make the person's hairs stand up because the charges in each hair push it away from the others, since whole body similar type of negative or positive charge.

Electric charge felt when one gets a shock from a doorknob or other object usually is between 25 thousand and 30 thousand volts.  However, the electric current only flows briefly, so the flow of electrons through the person's body does not cause physical harm.  On the other hand, when clouds gain electrical charges they have even higher voltages and the amperage (the number of electrons that will flow in the lightning strike) can be very high. That means that electrons can jump from a cloud to the earth (or from the earth to a cloud).  If those electrons go through a person, then the electric shock can burn or kill. It is the number of amperes that is harmful not the voltage.

## Historical experiment

The following experiment is described by James Clerk Maxwell in his work _A Treatise on Electricity and Magnetism_ (1873). Normally, glass and resin are both neutrally charged. However, if they are rubbed together and then separated, they will become able to attract each other.

If a second piece of glass is rubbed with a second piece of resin, the following things will be seen:

1. The two pieces of glass repel each other.
1. Each piece of glass attracts each piece of resin.
1. The two pieces of resin repel each other.

If a charged and an uncharged object are brought together, attraction will be very weak.

Bodies that are able to attract or repel things in this way are said to be 'electrified', or to be 'charged with electricity'. When two different substances are rubbed together, an electrical charge is produced because one of them will give electrons to the other. The reason is that the atoms in the two substances have unequal power to attract electrons. So the one that is more able to attract electrons will take electrons from the one that has a lower attractive force. If glass is rubbed against something else, it may either give or take electrons. What happens depends on what the other thing is.

Things that have taken electrons are called "negatively charged", and things that have given up electrons are called "positively charged". There is no special reason for these names. It is just an arbitrary (random choice) convention (agreement).

Besides being electrified by friction, bodies may be electrified in many other ways.

## Related pages

- Electric
- Static electricity