# Voltage

potential differenceVvoltageselectric potential differencepotentialdifference of potentialelectric tensionmVvoltelectric voltage
Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential between two points.wikipedia
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### Volt

VkVvolts
In the International System of Units, the derived unit for voltage is named volt.
The volt (symbol: V) is the derived unit for electric potential, electric potential difference (voltage), and electromotive force.

### Work (electrical)

workelectrical workelectrical
The difference in electric potential between two points (i.e., voltage) in a static electric field is defined as the work needed per unit of charge to move a test charge between the two points.

### Kirchhoff's circuit laws

Kirchhoff's current lawKirchhoff's voltage lawKirchhoff's laws
, but more often simply as V, for instance in the context of Ohm's or Kirchhoff's circuit laws.
Kirchhoff's circuit laws are two equalities that deal with the current and potential difference (commonly known as voltage) in the lumped element model of electrical circuits.

### Watt

kWMWmegawatt
The official SI definition for volt uses power and current, where 1 volt = 1 watt (of power) per 1 ampere (of current).
In terms of electromagnetism, one watt is the rate at which electrical work is performed when a current of one ampere (A) flows across an electrical potential difference of one volt (V), meaning the watt is equivalent to the volt-ampere (the latter unit, however, is used for a different quantity from the real power of an electrical circuit).

### International System of Units

SISI unitsSI unit
In the International System of Units, the derived unit for voltage is named volt.
The fourth unit could be chosen to be electric current, voltage, or electrical resistance.

### Joule

JkJMJ
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).

### Vacuum tube

vacuum tubestubethermionic valve
Even today, the term "tension" is still used, for example within the phrase "high tension" (HT) which is commonly used in thermionic valve (vacuum tube) based electronics.
In electronics, a vacuum tube, an electron tube, or valve (British usage) or, colloquially, a tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.

### SI derived unit

derived unitderived unitsJ/kg
In the International System of Units, the derived unit for voltage is named volt.

### Electric current

currentelectrical currentcurrents
Electric potential differences between points can be caused by electric charge, by electric current through a magnetic field, by time-varying magnetic fields, or some combination of these three.
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points.

### Inductor

inductorscoilinductive
If this definition of voltage is used, any circuit where there are time-varying magnetic fields, such as circuits containing inductors, will not have a well-defined voltage between nodes in the circuit.
When the current flowing through an inductor changes, the time-varying magnetic field induces an electromotive force (e.m.f.) (voltage) in the conductor, described by Faraday's law of induction.

### Electric field

electricelectrostatic fieldelectrical field
The difference in electric potential between two points (i.e., voltage) in a static electric field is defined as the work needed per unit of charge to move a test charge between the two points.
It can be approximated by placing two conducting plates parallel to each other and maintaining a voltage (potential difference) between them; it is only an approximation because of boundary effects (near the edge of the planes, electric field is distorted because the plane does not continue).

### Electrical engineering

electrical engineerelectricalElectrical and Electronics Engineering
In circuit analysis and electrical engineering, the voltage across an inductor is not considered to be zero or undefined, as the standard definition would suggest.
Notable developments in this century include the work of Hans Christian Ørsted who discovered in 1820 that an electric current produces a magnetic field that will deflect a compass needle, of William Sturgeon who, in 1825 invented the electromagnet, of Joseph Henry and Edward Davy who invented the electrical relay in 1835, of Georg Ohm, who in 1827 quantified the relationship between the electric current and potential difference in a conductor, of Michael Faraday (the discoverer of electromagnetic induction in 1831), and of James Clerk Maxwell, who in 1873 published a unified theory of electricity and magnetism in his treatise Electricity and Magnetism.

### Network analysis (electrical circuits)

circuit theorycircuit analysisnetwork analysis
In circuit analysis and electrical engineering, the voltage across an inductor is not considered to be zero or undefined, as the standard definition would suggest.
Two circuits are said to be equivalent with respect to a pair of terminals if the voltage across the terminals and current through the terminals for one network have the same relationship as the voltage and current at the terminals of the other network.

### Magnetic field

magnetic fieldsmagneticmagnetic flux density
Electric potential differences between points can be caused by electric charge, by electric current through a magnetic field, by time-varying magnetic fields, or some combination of these three.
:where is the electromotive force (or EMF, the voltage generated around a closed loop) and

### Electromotive force

EMFelectromotive force (EMF)
A voltage may represent either a source of energy (electromotive force) or lost, used, or stored energy (potential drop).
The electric charge that has been separated creates an electric potential difference that can be measured with a voltmeter between the terminals of the device.

### Ground (electricity)

groundgroundinggrounded
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.
Voltage is defined as a difference of electric potentials.

### Alternating current

ACalternating-currentalternating
When talking about alternating current (AC) there is a difference between instantaneous voltage and average voltage.
The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage.

### Oscilloscope

oscilloscopesoscillographcathode ray oscilloscope
Instruments for measuring voltages include the voltmeter, the potentiometer, and the oscilloscope.
An oscilloscope, previously called an oscillograph, and informally known as a scope or o-scope, CRO (for cathode-ray oscilloscope), or DSO (for the more modern digital storage oscilloscope), is a type of electronic test instrument that graphically displays varying signal voltages, usually as a two-dimensional plot of one or more signals as a function of time.

### Ohm's law

ohmicOhmohmic losses
, but more often simply as V, for instance in the context of Ohm's or Kirchhoff's circuit laws.
Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points.

### Direct current

DCdirect-currentDC current
Instantaneous voltages can be added for direct current (DC) and AC, but average voltages can be meaningfully added only when they apply to signals that all have the same frequency and phase.
The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage.

### Electric battery

batterybatteriesBattery (electricity)
The volt is named in honour of the Italian physicist Alessandro Volta (1745–1827), who invented the voltaic pile, possibly the first chemical battery.
The voltage developed across a cell's terminals depends on the energy release of the chemical reactions of its electrodes and electrolyte.

### Electric power

powerelectrical powerelectrical
(See "electric power".)
Electric power is transformed to other forms of energy when electric charges move through an electric potential (voltage) difference, which occurs in electrical components in electric circuits.

### Electrical injury

electric shockelectrocutionelectrocuted
In cases of exposure to high voltages, such as on a power transmission tower, physical contact with energized wiring or objects may not be necessary to cause electric shock, as the voltage may be sufficient to "jump" the air gap between the electrical device and the victim.

### Mains electricity by country

electric power systemsMains power systemsList of countries with mains power plugs, voltages and frequencies
Mains electricity by country includes a list of countries and territories, with the plugs, voltages and frequencies they commonly use for providing electrical power to appliances, equipment, and lighting typically found in homes and offices.

### Mains electricity

mainsmains powerelectricity supply
The two principal properties of the electric power supply, voltage and frequency, differ between regions.