Voltage Explained - What is Voltage? Basic electricity potential difference.
Voltage is the pressure from an electrical circuit's power source that pushes charged electrons (current) through a conducting loop, enabling them to do work such as illuminating light.
In brief, voltage = pressure, and it is measured in volts (V). The term recognises Italian physicist Alessandro Volta (1745-1827), inventor of the voltaic pile—the forerunner of today's household battery.
Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential between two points, which (in a static electric field) is defined as the work needed per unit of charge to move a test charge between the two points. The derived unit for voltage (potential difference) is named volt in the International System of Units. In SI units, work per unit charge is expressed as joules per coulomb, where 1 volt = 1 joule (of work) per 1 coulomb (of charge). The old SI definition for volt used to power and current; starting in 1990, the quantum Hall and Josephson effect was used, and recently (2019), fundamental physical constants have been introduced to define all SI units and derived units. A voltage or electric potential difference is denoted symbolically by ∆V, simplified V, or U, for instance, in Ohm's or Kirchhoff's circuit laws.
Electric potential differences between points can be caused physically by electric charge build-up or imbalance (e.g. well known "static" and electronic capacitor) also by an electric current through a magnetic field, and by time-varying magnetic fields (e.g. dynamo or generator), or some combination of these three. Additionally, on a macroscopic scale, potential differences can be caused by electrochemical processes (cells and batteries), pressure-induced piezoelectric effect, and heat-induced emf across metal-metal junctions. These latter processes at the microscopic level have the physical origins previously mentioned. A voltmeter can be used to measure the voltage (or potential difference) between two points in a system; often, a common reference potential such as the ground of the system is used as one of the points. A voltage may represent either a source of energy (electromotive force) or lost, used, or stored energy (potential drop).
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