Electric charge is a fundamental physical property of matter that dictates interaction with an electromagnetic field. This property is the source of the electric force, one of the four fundamental forces in the universe. When an object possesses this property, it experiences a force when placed near other charged objects. There are only two types of electric charge.
The Two Fundamental Types
The two distinct forms of electric charge are known as positive and negative. This nomenclature was an arbitrary assignment made by Benjamin Franklin to represent their opposing natures. Franklin’s choice of “plus” and “minus” was a simple way to mathematically represent the two observed electrical behaviors.
These two types of charge will always cancel each other out when they are present in equal amounts. When an object contains an exact balance of both, it is described as electrically neutral, possessing zero net charge.
The total electric charge of a macroscopic object is the algebraic sum of all the positive and negative charges contained within it. The imbalance, or the non-zero sum, determines if an object is “charged.”
Rules of Interaction
The two types of electric charge follow a strict set of rules that govern all electrical phenomena. Charges that are alike repel each other, while charges that are opposite attract each other. A positive charge repels another positive charge, and a negative charge similarly repels another negative charge.
Conversely, opposite charges brought into proximity will pull toward one another. The force of this attraction or repulsion operates across empty space without the objects needing to touch.
This force is mediated by an electric field, a physical field that surrounds every charged particle. The field extends outward, acting as the medium through which one charge exerts a force on another. The strength of this electric force diminishes rapidly as the distance between the two charges increases, a relationship described by Coulomb’s Law.
Where Charge Resides
The source of these two charge types lies within the fundamental building blocks of all matter, the atom. Two types of subatomic particles carry electric charge: protons and electrons. Protons, which reside in the nucleus, possess the positive charge.
Electrons, which orbit the nucleus, carry the negative charge. The magnitude of the charge on a single proton exactly equals the magnitude of the charge on a single electron, though their signs are opposite. This equality is why an ordinary atom with an equal number of protons and electrons is electrically neutral.
An object acquires a net electric charge when this balance is disturbed, typically through the transfer of electrons, which are much more mobile than the protons locked in the nucleus.
If an object gains extra electrons, it develops a negative charge. Conversely, if an object loses electrons, it results in a net positive charge. This process of gaining or losing electrons is known as ionization, and the resulting charged atom or molecule is called an ion.