Electric charge is a fundamental physical property of matter that governs its behavior in an electromagnetic field. It is the source of the force that drives many everyday phenomena, from lightning to the power flowing through an electrical circuit. An object possessing this property will experience a force when placed within an electric or magnetic field.
The Two Primary Types of Charge
All electric charge falls into one of two distinct categories: positive and negative. These terms were established as an arbitrary convention centuries ago to differentiate between the two opposing behaviors. The naming is credited to Benjamin Franklin in the 18th century, who needed labels to distinguish the two states he observed while experimenting with electricity.
Franklin assigned the label “positive” to the charge that accumulated on a glass rod rubbed with silk, and “negative” to the charge on amber rubbed with fur. His choice was based on a single-fluid theory of electricity. While the underlying theory was later proven incorrect, the algebraic labels of positive and negative stuck and are now universally used. Equal amounts of positive and negative charge combine or cancel each other out, resulting in a net charge of zero, which is called electrically neutral.
The Fundamental Rule of Interaction
The existence of two types of charge establishes the law of charges, which dictates how charged objects interact. This rule states that charges of the same type exert a repulsive force, while charges of opposite types exert an attractive force. Two positive charges or two negative charges placed near each other will push away.
Conversely, a positive charge and a negative charge brought into proximity will pull toward each other. This force causes phenomena like static cling. The strength of this attraction or repulsion depends on both the magnitude of the charges and the distance between them.
Charge in Atomic Structure
The two types of electric charge have their physical basis within the subatomic particles that make up all matter. The particles responsible for carrying these charges are protons and electrons. Protons, which reside in the atom’s nucleus, possess the positive electric charge.
Electrons, which orbit the nucleus, carry an equal magnitude of the negative electric charge. The third primary subatomic particle, the neutron, is electrically neutral, meaning it carries no net charge. In any neutral atom, the number of protons equals the number of electrons, causing their charges to perfectly balance out.
A net electric charge on an object results from an imbalance between its protons and electrons. An object that has gained extra electrons will possess a net negative charge, while an object that has lost electrons will be left with a net positive charge. Atoms that have gained or lost electrons are called ions, and the movement of these charged particles constitutes electric current.