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Josephson junction array chip developed by NIST as a standard volt.

The volt (symbol: V) is the SI derived unit of electromotive force, commonly called "voltage".[1] It is also the unit for the related but slightly different quantity electric potential difference (also called "electrostatic potential difference"). It is named in honor of the Italian physicist Alessandro Volta (1745–1827), who invented the voltaic pile, possibly the first chemical battery.

Contents

Definition

The volt is defined as the value of the voltage across a conductor when a current of one ampere dissipates one watt of power in the conductor. [2] It can be written in terms of SI base units as: m2 · kg · s−3 · A−1. It is also equal to one joule of energy per coulomb of charge, J/C.

\mbox{V} = \dfrac{\mbox{W}}{\mbox{A}} = \dfrac{\mbox{J}}{\mbox{A} \cdot \mbox{s}} = \dfrac{\mbox{N} \cdot \mbox{m} }{\mbox{A} \cdot \mbox{s}} = \dfrac{\mbox{kg} \cdot \mbox{m}^2}{\mbox{A} \cdot \mbox{s}^{3}} = \dfrac{\mbox{kg} \cdot \mbox{m}^2}{\mbox{C} \cdot \mbox{s}^2} = \dfrac{\mbox{N} \cdot \mbox{m}} {\mbox{C}} = \dfrac{\mbox{J}}{\mbox{C}}
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Josephson junction definition

Since 1990 the volt has been maintained internationally for practical measurement using the Josephson effect, where a conventional value is used for the Josephson constant, fixed by the 18th General Conference on Weights and Measures as:

K{J-90} = 0.4835979 GHz/µV.

Water flow analogy

In the water flow analogy sometimes used to explain electric circuits by comparing them to water-filled pipes, voltage difference is likened to water pressure difference – the difference determines how quickly the electrons will travel through the circuit. Current (in amperes), in the same analogy, is a measure of the volume of water that flows past a given point per unit time (volumetric flow rate). The flow rate is determined by the width of the pipe (analogous to electrical resistance), and the pressure difference between the front end of the pipe and the exit is analogous to voltage. The analogy extends to power dissipation: the power given up by the water flow is equal to flow rate times pressure, just as the power dissipated in a resistor is equal to current times the voltage drop across the resistor (amperes x volts = watts).

The relationship between voltage and current (in ohmic devices) is defined by Ohm's Law.

Common voltages

A multimeter can be used to measure the voltage between two positions.
1.5 V C-cell batteries

Nominal voltages of familiar sources:


Note: Where RMS (root mean square) is stated above, the peak voltage is \sqrt{2} times greater than the RMS voltage for a sinusoidal signal centered around zero voltage.

History of the volt

In 1800, as the result of a professional disagreement over the galvanic response advocated by Luigi Galvani, Alessandro Volta developed the so-called Voltaic pile, a forerunner of the battery, which produced a steady electric current. Volta had determined that the most effective pair of dissimilar metals to produce electricity was zinc and silver. In the 1880s, the International Electrical Congress, now the International Electrotechnical Commission (IEC), approved the volt as the unit for electromotive force. At that time, the volt was defined as the potential difference [i.e., what is nowadays called the "voltage (difference)"] across a conductor when a current of one ampere dissipates one watt of power.

The international volt was defined in 1893 as 1/1.434 of the emf of a Clark cell. This definition was abandoned in 1908 in favor of a definition based on the international ohm and international ampere until the entire set of "reproducible units" was abandoned in 1948.

Prior to the development of the Josephson junction voltage standard, the volt was maintained in national laboratories using specially constructed batteries called standard cells. The United States used a design called the Weston cell from 1905 to 1972.

This SI unit is named after Alessandro Volta. As with every SI unit whose name is derived from the proper name of a person, the first letter of its symbol is uppercase (V). When an SI unit is spelled out in English, it should always begin with a lowercase letter (volt), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius" conforms to this rule because the "d" is lowercase.
Based on The International System of Units, section 5.2.

See also

References

  1. ^ "SI Brochure, Table 3 (Section 2.2.2)". BIPM. 2006. http://www.bipm.org/en/si/si_brochure/chapter2/2-2/table3.html. Retrieved 2007-07-29.  
  2. ^ BIPM SI Brochure: Appendix 1, p. 144
  3. ^ Bullock, Orkand, and Grinnell, pp. 150–151; Junge, pp. 89–90; Schmidt-Nielsen, p. 484

External links


Quotes

Up to date as of January 14, 2010
(Redirected to Plug-in hybrid article)

From Wikiquote

This page contains quotes and slogans about plug-in hybrid electric vehicles.

Contents

General (sourced)

  • "Possibly the most sought-after technological innovation since Captain Kirk first flipped open his communicator is the plug-in hybrid."
- Matthew L. Wald, "A Plug-In Conversion for Prius", The New York Times, 2008-04-27 [1].
- "The end of the petrolhead", The Economist, 2008-06-19 [2]
  • "The drumbeat of the electrical transportation is accelerating like nothing I've ever seen in my life."
- Andrew Grove, "Ex-Intel head pushes electric cars", Associated Press by Ken Thomas, 2008-06-27 [3]
  • "While the ability for Obama, if elected, to deliver on his energy-related campaign promises remains to be seen, Tuesday night's presentations helped establish the plug-in hybrid as a mainstream American household term perhaps as a synonym for 100-mpg vehicle."
-Bradley Berman, "Democrats Put Plug-In Hybrids on Main Stage" Hybridcars.com, 2008-08-27 [4]
  • "Felix Kramer, who has made plug-in electric cars not only his passion but an imminent American reality, was always ready to take a query from me."
- Thomas L. Friedman of The New York Times, "Hot, Flat and Crowded: Why We Need a Green Revolution and How It Can Renew America", page 417, 2008-09-09.

"The plug-in hybrid is the most notable technological advancement of the past 50 years", "G.M.'s challenge is making them profitable and continuing to invent a broad range of advanced vehicles."

-David Cole, the chairman of the Center for Automotive Research in "G.M. at 100: Is Its Future Electric?", The New York Times by Don Sherman, 2008-09-14

About brands

General Motors

Chevrolet Volt

"The Chevrolet Volt has joined baseball and apple pie as an unassailable, non-partisan symbol of American can-do and know-how. General Motors won't start selling the plug-in hybrid for another 18 months (at least), but that hasn't kept it from becoming the most important political accessory since the flag lapel pin."

-Chuck Squatriglia/Keith Barry, "McCain Announces His Running Mate - The Chevy Volt" Wired.com, 2008-07-18 [5].
  • Volt is the GM's "most important model in decades -- and possibly the key to its survival."
- John D. Stoll, "GM Looks for Buzz With Its Electric Volt; Auto Maker Hopes High-Mileage Car Will Repair Image", Wall Street Journal, 2008-09-15[6].
  • "It represents nothing less than the first step in the reinvention of the automobile." [7]
Bob Lutz, GM Fastlane Blog "Power On", September 16th, 2008
  • "It's not a car for everyone, but it's the first step toward a new kind of car for everyone".
Mark Phelan, "Chevy Volt's value is as dawn of era", Detroit Free Press , 2008-09-21 [8]

References

  1. http://www.nytimes.com/2008/04/27/automobiles/27PLUGIN.html
  2. http://www.economist.com/­specialreports/­PrinterFriendly.cfm?story_id=11565627
  3. http://www.chicagotribune.com/­news/­chi-ap-grove-plug-ins,0,1749993.story
  4. http://www.hybridcars.com/­incentives-laws/­democrats-put-plug-hybrids-main-stage-24908.html
  5. http://blog.wired.com/cars/2008/07/mccain-announce.html
  6. http://online.wsj.com/­article/­SB122143673862434189.html
  7. http://fastlane.gmblogs.com/archives/2008/09/power_on.html
  8. http://www.freep.com/apps/pbcs.dll/article?AID=/20080921/COL14/809210488&imw=Y

Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

See also volt

German

Noun

Volt

  1. volt (unit of measure)

This German entry was created from the translations listed at volt. It may be less reliable than other entries, and may be missing parts of speech or additional senses. Please also see Volt in the German Wiktionary. This notice will be removed when the entry is checked. (more information) January 2009


Simple English

[[File:|thumb|Josephson junction array chip developed by NIST as a standard volt.]]

For the electric plug-in hybrid concept car, see Chevrolet Volt.
For the record label, see Volt Records

The volt (symbol: V) is the SI derived unit of electric potential difference or electromotive force [1]. It is named in honor of the Italian physicist Alessandro Volta (1745–1827), who invented the voltaic pile, the first chemical battery.

Contents

Definition

The volt is defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power. Hence, it is the base SI representation m2 · kg · s-3 · A-1, which can be equally represented as one joule of energy per coulomb of charge, J/C.

\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}}

Hydraulic analogy

In the hydraulic analogy sometimes used to explain electric circuits by comparing them to water-filled pipes, voltage is likened to water pressure - it determines how fast the electrons will travel through the circuit. Current (in amperes), in the same analogy, is a measure of the volume of water that flows past a given point, the rate of which is determined by the voltage, and the total output measured in watts. The equation that brings all three components together is: volts × amperes = watts

Common voltages

File:Electronic multi
A multimeter can be used to measure the voltage between two points

[[File:|150px|thumb|1.5 V C-cell batteries]]

Nominal voltages of familiar sources:

  • Nerve cell action potential: around 30 mV
  • Single-cell, rechargeable NiMH or NiCd battery: 1.2 V
  • Mercury battery 1.355 V
  • Single-cell, non-rechargeable alkaline battery (e.g. AAA, AA, C and D cells): 1.5 V
  • Lithium polymer rechargeable battery: 3.75 V
  • Transistor-transistor logic (TTL) power supply: 5 V
  • PP3 battery: 9 V
  • Automobile electrical system: 12 V (nominal)
  • Household mains electricity: 230 V RMS in Europe, Australia, Asia and Africa, 120 V RMS in North America, 100 V RMS in Japan (see List of countries with mains power plugs, voltages and frequencies)
  • Rapid transit third rail: 600 to 700 V (see List of current systems for electric rail traction)
  • High speed train overhead power lines: 25 kV RMS at 50 Hz, but see List of current systems for electric rail traction for exceptions.
  • High voltage electric power transmission lines: 110 kV RMS and up (1150 kV RMS is the record as of 2005)
  • Lightning: Varies greatly, often around 100 MV.

Note: Where 'RMS' (root mean square) is stated above, the peak voltage is \sqrt{2} times greater than the RMS voltage for a sinusoidal signal.

History of the volt

In 1800, as the result of a professional disagreement over the galvanic response advocated by Luigi Galvani, Alessandro Volta developed the so-called Voltaic pile, a forerunner of the battery, which produced a steady electric current. Volta had determined that the most effective pair of dissimilar metals to produce electricity was zinc and silver. In the 1880s, the International Electrical Congress, now the International Electrotechnical Commission (IEC), approved the volt for electromotive force. The volt was defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power.

Other pages

References

  1. Rudolf F. Graf, "Volt", Dictionary of Electronics; Radio Shack, 1974-75. Fort Worth, Texas. ISBN B000AMFOZY
krc:Вольт


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