Electricity is the set of physical phenomena associated with the presence and motion of electric charge. Although initially considered a phenomenon separate from magnetism, since the development of Maxwell’s Equations both are recognized as part of a single electromagnetic field. Electricity is caused by static electricity or moving electrons in an conductor. The presence of an electric field indicates the potential for electricity to flow; an electric current is produced when this potential difference across a conductive material is actualized by movement of charges through that material (electrical conduction).
In materials not considered to be good conductors of electricity (such as insulators), electrons may flow freely under the influence of an applied voltage, but only do so if that voltage exceeds a threshold value known as the breakdown voltage. If there is no net movement of charges—that is, if the voltages applied across a material are equal and opposite and there are no other sources or sinks for charge within that material—then it is said to be in electrostatic equilibrium. When two materials are in contact, charges may redistribute such that one object gains a net charge while the other loses an equal amount, but this redistribution doesn’t necessarily result in net current flow between those objects because it doesn’t involve charge flowing through a conducting medium. This type of charging is called triboelectric charging, and can happen due to friction (for example, when walking on carpet and then touching a metal door handle) or simply due to contact with another object (like picking up a stone off the ground).
The study of electricity dates back to antiquity, though progress was largely limited until early modern times due to limitations on understanding of electrical phenomena. Experimental work began in earnest after Michael Faraday discovered electromagnetic induction in 1831, opening up new avenues for research into electrical phenomena. Mathematical modeling was also essential for understanding how electricity behaves—James Clerk Maxwell’s equations describing electromagnetism were first published in 1865 and have been fundamental ever since.
Since then our knowledge and utilization of electricity has grown exponentially; it now forms the basis for most modern technologies including computers, telecommunications, lighting, motors and many more applications too numerous to list here. In fact, it would be difficult to overstate the importance of electricity in our lives today!