Volt

volt
volt
	B, V
Value	electric potential electric voltage electromotive force
System	SI
Type of	derivative

Volt (Russian designation: B ; international: V ) - in the International System of Units (SI), a unit of measurement of electric potential , potential difference , electric voltage and electromotive force . It was named after the Italian physicist and physiologist Alessandro Volta (1745-1827), who invented the first electric battery - the voltaic pole and published the results of his experiments in 1800 .

The potential difference between two points is 1 volt, if to move a charge of 1 pendant from one point to another, work on it must be done in the amount of 1 joule . A volt is also equal to the electric voltage causing a direct current of 1 ampere at a power of 1 watt in the electric circuit.

In accordance with SI rules regarding derivative units named after scientists, the name of a volt unit is written with a lowercase letter , and its designation with a capital letter . This spelling of the designation is also preserved in the designations of derived units formed using volts. For example, the designation of the unit of measurement of the electric field "volt per meter " is written as V / m.

1 V = (1/300) units GHSE potential ^[1] .

Content

Definition

Volt (V, V) can be defined either as the electric voltage at the ends of the conductor , necessary for the release of heat in it with a power of one watt (W, W) with a direct current flowing through this conductor of one ampere (A), or as the difference potentials between two points of the electrostatic field , during the passage of which over a charge of 1 pendant (C, C) a work of 1 joule (J, J) is performed, or as a potential difference across a resistor of 1 Ohm (Ω) with a current flowing through it of 1 amperes ^[2] . Expressed through the basic units of the SI system, one volt is equal to m ² · kg · s ⁻³ · A ⁻¹ .

{\mbox{V}}={\dfrac {\mbox{W}}{\mbox{A}}}={\dfrac {\mbox{J}}{\mbox{C}}}={\dfrac {{\mbox{m}}^{2}\cdot {\mbox{kg}}}{{\mbox{s}}^{3}\cdot {\mbox{A}}}}={\mbox{A}}\cdot {\mbox{Ω}}.

{\ displaystyle {\ mbox {V}} = {\ dfrac {\ mbox {W}} {\ mbox {A}}} = {\ dfrac {\ mbox {J}} {\ mbox {C}}} = { \ dfrac {{\ mbox {m}} ^ {2} \ cdot {\ mbox {kg}}} {{\ mbox {s}} ^ {3} \ cdot {\ mbox {A}}}} = {\ mbox {A}} \ cdot {\ mbox {Ω}}.}

Determination Based on the Josephson Effect

A matrix of Josephson contacts developed by the National Institute of Standards to reproduce standard volts.

Since 1990, the volt has been standardized through measurement using the non-stationary Josephson effect , in which the Josephson constant , fixed by the 18th General Conference on Weights and Measures as ^{[3], is} used to bind to the standard:

K_{J-90}={\frac {2e}{h}}=

{\ displaystyle K_ {J-90} = {\ frac {2e} {h}} =}

0.4835979 GHz / μV,

where e is the elementary charge , h is the Planck constant

With this method, the volt value is uniquely associated with the frequency standard specified by the cesium clock : when a matrix consisting of several thousand Josephson junctions is irradiated with microwave radiation at frequencies from 10 GHz to 80 GHz, a quite definite voltage is generated by which voltmeters are calibrated ^[4] . The experiments showed that this method is insensitive to a specific implementation of the installation and does not require the introduction of correction factors ^[5] .

Voltage Scale

The smallest measured voltage is about 10 nV.
The sensitivity of the connected equipment when working with voice is 1 ... 1.5 μV (one of the weakest signals that are currently widely used)
The output voltage at the magnetic head of the cassette recorder is 0.3 mV ^[6] .
The potential difference on the neuron membrane is 70 mV.
NiCd battery - 1.2 V.
The alkaline element is 1.5 V.
The lithium iron phosphate battery (LiFePO ₄ ) is 3.3 V.
The charger for mobile phones is 5.0 V.
Battery "Krona" - 9 V.
Car battery - 12 V (for heavy trucks - 24 V).
The voltage of a household network in Russia is 230 V (phase), 400 V (linear).
Voltage in industrial networks - 400 V (three-phase), 400 V (single-phase), 690 V (three-phase)
The voltage in the contact network of the tram and trolleybus is 600 V (660 V) (direct current).
Contact rail voltage in the subway - 825 V (DC) .
Electrified Railways - 3 kV (direct current), 25 kV (alternating current).
Trunk power lines - 110, 220, 330, 500, 750 and 1150 kV.
The highest direct voltage obtained in the laboratory on a pelletron is 25 MV.
Lightning - from 100 MV and higher.

Historical background

The unit of measurement "volts" was introduced in 1861 by the committee of electrical standards created by William Thomson . Its introduction was related to the current needs of engineering physics. On June 1, 1898, by imperial law in Germany, 1 volt was established as a “legal” unit of measurement of EMF , equal to EMF, exciting a current of 1 ampere in a conductor with a resistance of 1 ohm ^[7] . Volt was introduced into the International System of Units (SI) by a decision of the XI General Conference on Weights and Measures in 1960 simultaneously with the adoption of the SI system as a whole ^[8] .

Subsequently, 1 volt was usually determined through a unit of energy joule and a unit of charge pendant .

Multiple and fractional units

Decimal multiple and fractional units are formed using standard SI prefixes .

Multiple				Equity
value	title	designation		value	title	designation
10 ¹ V	decavolt	yes	daV	10 ⁻¹ V	decivolt	dv	dV
10 ² V	hectovolt	GV	hV	10 ⁻² V	centivolt	cb	cV
10 ³ V	kilovolt	kV	kV	10 ⁻³ V	millivolt	mV	mV
10 ⁶ V	megavolt	MV	MV	10 ⁻⁶ V	microvolt	μV	µV
10 ⁹ V	gigavolt	GW	Gv	10 ⁻⁹ V	nanovolt	nV	nV
10 ¹² V	teravolt	Tv	Tv	10 ⁻¹² V	povolt	pv	pV
10 ¹⁵ V	petavolt	PV	PV	10 ⁻¹⁵ V	femtovolt	fv	fV
10 ¹⁸ V	exavolt	EV	EV	10 ⁻¹⁸ V	attovolt	aB	aV
10 ²¹ V	zettavolt	ST	Zv	10 ⁻²¹ V	zeptovolt	ZV	zV
10 ²⁴ V	iottavolt	IW	Yv	10 ⁻²⁴ V	ioctovolt	IV	yV
not recommended

Notes

↑ I.V. Saveliev . General physics course. - T. II. Electricity. - S. 41.
↑ Sivukhin D.V. General course of physics. - M .: Nauka , 1977 .-- T. III. Electricity. - S. 196. - 688 p.
↑ Representation of the volt by means of the Josephson effect // BIPM
↑ Burroughs, CJ, Benz, SP, Harvey, TE, Hamilton, CA 1 Volt DC Programmable Josephson Voltage Standard System (English) // IEEE Transactions on Applied Superconductivity. - 1999. - Vol. 9. - P. 4145-4148.
↑ Mark W. Keller. Current status of the quantum metrology triangle // Metrologia . - 2008 .-- Vol. 45. - P. 102. - DOI : 10.1088 / 0026-1394 / 45/1/014 .
↑ Magnetic heads for cassette recorders
↑ V. M. Dukov. History of systems of units of measurement of physical quantities Archival copy of January 26, 2012 on the Wayback Machine // From the book. “Historical reviews in the course of high school physics” ( M .: Education, 1983)
↑ Resolution 12 of the 11th meeting of the CGPM (1960 ) on the website of the International Bureau of Weights and Measures

[1] I.V. Saveliev . General physics course. - T. II. Electricity. - S. 41.

[2] Sivukhin D.V. General course of physics. - M .: Nauka , 1977 .-- T. III. Electricity. - S. 196. - 688 p.

[3] Representation of the volt by means of the Josephson effect // BIPM

[4] Burroughs, CJ, Benz, SP, Harvey, TE, Hamilton, CA 1 Volt DC Programmable Josephson Voltage Standard System (English) // IEEE Transactions on Applied Superconductivity. - 1999. - Vol. 9. - P. 4145-4148.

[5] Mark W. Keller. Current status of the quantum metrology triangle // Metrologia . - 2008 .-- Vol. 45. - P. 102. - DOI : 10.1088 / 0026-1394 / 45/1/014 .

[6] Magnetic heads for cassette recorders

[7] V. M. Dukov. History of systems of units of measurement of physical quantities Archival copy of January 26, 2012 on the Wayback Machine // From the book. “Historical reviews in the course of high school physics” ( M .: Education, 1983)

[8] Resolution 12 of the 11th meeting of the CGPM (1960 ) on the website of the International Bureau of Weights and Measures