Long before any physical understanding of electricity existed, people were aware of shocks delivered by electric fish, such as the Nile catfish and the electric eel, as well as the atmospheric discharge of lightning.¹⁹²⁰ Around 600 BCE, the Greek philosopher Thales of Miletus observed that rubbing amber—known in Greek as elektron—with fur or silk caused the fossilized resin to attract light objects such as feathers and straw, documenting what is now known as static electricity.²¹ For more than two millennia, this phenomenon remained little more than a philosophical curiosity.

Systematic scientific inquiry began in 1600, when the English physician William Gilbert published De Magnete, in which he distinguished the lodestone effect of magnetism from the static attraction of rubbed amber. Gilbert coined the Neo-Latin term electricus, meaning "of amber" or "like amber," giving rise to the English words "electric" and "electricity".²² In 1660, Otto von Guericke invented an early electrostatic generator using a rotating sulfur globe, and in 1675 Robert Boyle demonstrated that electrical attraction and repulsion act across a vacuum. In 1729, Stephen Gray classified materials into conductors, which allow charge to flow, and nonconductors or insulators, which inhibit its movement. Soon after, Charles François de Cisternay du Fay identified two distinct types of electricity, which he termed "vitreous" and "resinous".

In the mid-eighteenth century, invention of the Leyden jar independently by Ewald Georg von Kleist and Pieter van Musschenbroek in 1745–1746 provided researchers with the first capacitor, capable of storing and discharging substantial quantities of static charge. In 1752, Benjamin Franklin conducted his famous kite experiment during a thunderstorm, demonstrating that lightning is an electrical discharge and establishing the convention of positive and negative charge within a single-fluid model of electricity. In 1785, Charles-Augustin de Coulomb published the inverse-square law governing electrostatic forces between charged bodies.²³

The transition from static electricity to continuous electric current occurred at the turn of the nineteenth century. Following Luigi Galvani's 1780s observations that electrical sparks caused frog legs to twitch—which Galvani attributed to "animal electricity"—Italian physicist Alessandro Volta demonstrated that the electricity originated from the chemical interaction of dissimilar metals separated by a moist intermediary. In 1800, Volta constructed the voltaic pile, the first chemical battery, which provided scientists with a steady source of electric current.

In 1820, Hans Christian Ørsted observed that an electric current in a wire deflected a nearby compass needle, establishing a direct link between electricity and magnetism. André-Marie Ampère rapidly formulated a mathematical description of the magnetic forces between current-carrying conductors, while Georg Simon Ohm in 1826–1827 quantified the relationship between potential difference, current, and resistance. In 1831, Michael Faraday discovered electromagnetic induction, showing that a changing magnetic field produces an electric potential in a conductor—the operating principle behind the electric generator and transformer. In 1861 and 1862, James Clerk Maxwell unified these experimental laws into a set of coupled differential equations, demonstrating that electric and magnetic fields travel through space as waves at the speed of light. Heinrich Hertz experimentally confirmed the existence of Maxwell's electromagnetic waves in the late 1880s, and in 1897 J. J. Thomson at Cambridge University discovered the electron, identifying the subatomic particle responsible for electric current in metals.²⁴

Electricity and magnetism are fundamentally interrelated aspects of a single electromagnetic force. Any moving electric charge, or electric current, generates a circular magnetic field in the space surrounding it. When a wire carrying a current is coiled into a solenoid, the magnetic fields of the individual loops combine to form an electromagnet, whose field strength can be amplified by inserting a ferromagnetic core such as iron. Conversely, a magnetic field exerts a mechanical force—known as the Lorentz force—on a moving charge or a current-carrying wire placed within it. This mutual interaction is the operating basis of the electric motor, which converts electrical energy into mechanical rotation.

Faraday's law of induction describes the inverse process: when the magnetic flux through a closed loop of wire changes over time—either because the magnetic field itself is varying or because the wire loop is moving through the field—an electromotive force (voltage) is induced in the wire. This principle allows mechanical energy to be converted into electrical energy in an electric generator. Furthermore, Maxwell's addition of the "displacement current" term to Ampère's circuital law revealed that a time-varying electric field generates a magnetic field even in the absence of moving charges.³¹ Together, Maxwell's four equations demonstrate that oscillating electric and magnetic fields continuously regenerate one another, propagating outward through a vacuum at roughly 300,000 kilometers per second as electromagnetic radiation, a spectrum that encompasses radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

In electrical engineering, electric power is the rate at which electrical energy is transferred by an electric circuit. Measured in watts (symbol W, equal to one joule per second), instantaneous electric power ($P$) in a direct-current circuit is calculated as the product of voltage and current ($P = V \times I$). Combining this relation with Ohm's law shows that the power dissipated as heat in a resistor of resistance $R$ is proportional to the square of the current ($P = I^2 R$). Because energy is power multiplied by time, commercial electrical energy consumption is typically billed in kilowatt-hours (kWh) or measured at the utility scale in megawatt-hours (MWh) and terawatt-hours (TWh).³²

During the 1880s and early 1890s, the commercialization of electric power sparked an industrial and technical rivalry known as the "War of the Currents".³³ American inventor Thomas Edison, who had developed a practical incandescent light bulb and opened the Pearl Street Station in New York in 1882, championed direct current (DC), in which electric charge flows steadily in one direction.³⁴ Serbian-born inventor Nikola Tesla and industrialist George Westinghouse advocated alternating current (AC), in which the flow of charge periodically reverses direction, typically 50 or 60 times per second (50 or 60 hertz) in modern grids.

The decisive advantage of alternating current lay in the transformer, a device operating on Faraday's principle of mutual induction that can efficiently step AC voltage up or down. Because power loss due to resistance in transmission lines is proportional to the square of the current ($I^2 R$), stepping a generator's output up to very high voltages reduces the current required to transmit a given amount of power, slashing energy losses over long distances. Edison's low-voltage DC system could only distribute power economically within a radius of about one mile (1.6 kilometers) from a generating station, whereas AC could be sent across hundreds of miles before being stepped down by local transformers to safer voltages for household and industrial use. Following Westinghouse's successful illumination of the 1893 World's Columbian Exposition in Chicago and the commissioning of the polyphase AC hydroelectric power plant at Niagara Falls in 1895, alternating current became the global standard for electrical grids.³⁵ In contemporary grids, high-voltage direct current (HVDC) is also deployed using modern power electronics for specialized point-to-point interconnections, such as long subsea cables and links between asynchronous AC networks.

Most utility-scale electricity is generated by electromechanical generators—known as turbo-alternators—driven by steam, gas, water, or wind turbines. In thermal power plants, heat produced by burning fossil fuels (coal, natural gas, or oil), biomass, or through nuclear fission boils water into high-pressure steam that spins a turbine connected to an AC generator. Hydroelectric dams and wind turbines convert the kinetic energy of flowing water and air directly into rotational motion. In contrast, solar photovoltaics (PV) generate direct current without moving parts via the photovoltaic effect in semiconductor cells, using inverters to convert the output into alternating current for the grid. Because electrical grids require supply and demand to remain in instantaneous balance to maintain stable voltage and frequency, grid operators increasingly pair variable renewable generators with grid-scale battery storage and pumped-storage hydroelectricity.³⁶³⁷

Electricity occurs abundantly in nature, most visibly as atmospheric lightning.³⁸ Within cumulonimbus storm clouds, turbulent updrafts and collisions between ice crystals and graupel separate electric charges, creating immense potential differences between different regions of a cloud or between the cloud base and the ground. When the electric field exceeds the dielectric breakdown strength of air, the air ionizes into a conductive plasma channel, resulting in a rapid electrical discharge. A typical lightning strike carries a current of approximately 30,000 amperes across a potential difference of several hundred million volts, lasting only a few milliseconds while heating the surrounding air to temperatures near 30,000 °C (50,000 °F), which causes the explosive shockwave heard as thunder. On a planetary scale, convective motion of molten iron and nickel in the Earth's outer core generates electric currents through dynamo action, sustaining the geomagnetic field.

In biology, bioelectricity is fundamental to cellular function in all living organisms. Unlike metallic conduction, which relies on free electrons, bioelectric currents consist of the movement of electrically charged ions—primarily sodium ($\text{Na}^+$), potassium ($\text{K}^+$), calcium ($\text{Ca}^{2+}$), and chloride ($\text{Cl}^-$)—across cell membranes. Specialized proteins called ion pumps and channels maintain concentration gradients across the lipid bilayer of cells, establishing a resting membrane potential typically ranging from a few millivolts to around 100 millivolts. In excitable tissues such as neurons and muscle fibers, rapid, transient reversals of this voltage—known as action potentials—propagate along cell membranes, enabling nerve impulse transmission, brain activity, and the coordinated contraction of skeletal and cardiac muscle. In clinical medicine, surface electrodes are routinely used to record these bioelectric potentials for diagnostic purposes, notably in electrocardiography (ECG) for the heart and electroencephalography (EEG) for the brain. Certain aquatic species, such as the electric eel (Electrophorus electricus), possess specialized electric organs composed of thousands of modified muscle cells (electroplaques) stacked in series and parallel, capable of discharging currents of up to one ampere at 600 to 1,000 volts to stun prey or deter predators.

Because the human nervous and muscular systems operate via minute electrical signals, externally applied electric currents passing through the body can cause severe injury or death—a hazard known as electric shock or, when fatal, electrocution. The physiological severity of an electric shock depends primarily on the magnitude of the current, its pathway through the body, its duration, and its frequency. Dry human skin offers relatively high resistance, whereas wet skin or internal tissues rich in conductive electrolytes offer much lower resistance. Currents of a few milliamperes produce a tingling sensation, while currents above 10 to 20 milliamperes can induce sustained, involuntary muscle contraction (tetany), preventing a victim from releasing an energized conductor and potentially paralyzing the respiratory muscles of the chest. Currents of roughly 50 to 100 milliamperes or more passing through the thorax can disrupt the heart's natural pacemaker rhythms, triggering ventricular fibrillation—an uncoordinated twitching of the heart ventricles that halts blood circulation and quickly proves fatal without defibrillation. Additionally, high-current discharges produce intense Joule heating ($I^2 R$) along their path, causing deep internal thermal burns and cellular breakdown.

Throughout the twentieth century and the first two decades of the twenty-first, global electricity production was dominated by the combustion of fossil fuels, particularly coal, which consistently generated roughly 40 percent of the world's electricity from the 1970s until the mid-2010s.³⁹ Because fossil-fuel power plants are the single largest source of anthropogenic carbon dioxide emissions—emitting approximately 14 billion tonnes of $\text{CO}_2$ in 2023—transitioning the global power sector to low-carbon sources and electrifying end-use sectors such as road transport, space heating, and industry have become central pillars of international climate policy.

In the mid-2020s, the global electricity mix reached a historical inflection point driven by the exponential expansion of solar photovoltaics and wind power.⁴⁰ According to the Global Electricity Review 2026 published by the energy think tank Ember and data from the International Energy Agency (IEA), global electricity demand rose by 849 TWh (2.8 percent) in 2025 to exceed 31,700 TWh.³⁷ For the first time in over a century—since a brief period in 1919 when early hydropower exceeded coal—combined renewable energy sources overtook coal to become the largest category of electricity generation worldwide. In 2025, renewables generated 10,730 TWh, accounting for 33.8 percent of global electricity, surpassing coal generation at 10,476 TWh (approximately 33 percent).⁴¹

Solar power served as the primary engine of this shift, increasing by a record 636 TWh (30 percent) in 2025 to reach 2,779 TWh, thereby meeting 75 percent of the world's total electricity demand growth on its own. Wind power rose by 205 TWh (8.2 percent) to reach 2,713 TWh, while nuclear power increased by 1.2 percent to reach a record high of 2,812 TWh following reactor restarts in Japan, strong output in France, and new grid connections in Asia. Together, total clean electricity generation—comprising solar, wind, hydroelectricity, bioenergy, and nuclear power—grew by 887 TWh in 2025, outpacing total demand growth and causing global fossil-fuel generation to decline by 0.2 percent. Notably, 2025 marked the first time in five decades that coal-fired power generation declined simultaneously in both China and India, falling by 56 TWh and 52 TWh respectively, as rapid renewable capacity additions outstripped domestic demand growth. This structural shift continued into 2026: in April 2026, combined global wind and solar output reached 531 TWh (22 percent of global electricity), surpassing natural gas generation at 477 TWh (20 percent) for the first month on record.⁴²