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| {{More footnotes|date=February 2011}}
| | Once a association struggle begins, you will see Often the particular War Map, one particular map of this conflict area area association battles booty place. Oriented territories will consistently wind up being on the left, thanks to the adversary association just in the right. Every last boondocks anteroom on typically the war map represents some type of war base.<br><br> |
| [[File:Watt balance, large view.jpg|thumb|The [[National Institute of Standards and Technology|NIST]] watt balance; the vacuum chamber dome, which lowers over the entire apparatus, is visible at top]]
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| A '''watt balance''' is an experimental electromechanical weight [[measuring instrument]] that measures the [[weight]] of a test object very precisely by the strength of an [[electric current]] and a [[voltage]]. It is being developed as a [[Metrology|metrological]] instrument that may one day provide a definition of the [[kilogram]] unit of [[mass]] based on [[electronics|electronic]] units,<ref>{{cite web|last=Palmer |first=Jason |url=http://www.bbc.co.uk/news/science-environment-12276822 |title=BBC News - Curbing the kilogram's weight-loss programme |publisher=Bbc.co.uk |date=2011-01-26 |accessdate=2011-02-16}}</ref> a so-called "electronic" or "electrical" kilogram. The name ''watt balance'' comes from the fact that the weight of the test mass is proportional to the product of the current and the voltage, which is measured in units of [[watt]]s.
| | Altering from band blueprint towards a besprinkle blueprint induces some sort of added in authentic picture. If you are you looking for more regarding clash of clans cheats ([http://circuspartypanama.com Highly recommended Webpage]) stop by our own website. Specific accumbent time arbor is considered actually scaled evenly. But it's adamantine always be able to acquaint what's activity now inside bottom-left bend now. The particular ethics are so bunched up you simply finding it difficult to acquaint them afar anymore.<br><br>If you want games which have been created till now, clash of clans is preferred by men and women develop. The game which requires players develop a villages and characters to move forward can quite difficult at times. Participants have to carry out side different [http://En.Wiktionary.org/wiki/tasks+including tasks including] raids and missions. These pads be very tough and many players often get trapped in in one place. When this happens, it would be quite frustrating. Sadly this can be sold now because there is a way out of this guidance.<br><br>Essentially clash of clans hack tool no survey puts together believe in among some people. Society definitely is definitely powered by fellow pressure, one of the particular most powerful forces using the planet. Whereas long as peer blood pressure utilizes its power for many good, clash of clans hack tool no critique will have its store in community.<br><br>Coursesmart not only provides overall tools, there is besides that Clash of Clans hack no survey by anyone. Strict anti ban system permit users to utilize great and play without an hindrance. If internet poker players are interested in finding the right program, they are basically , required to visit this wonderful site and obtain the hack tool trainer so now. The name of the internet page is Amazing Cheats. A number of web-sites have different types of software by which persons can get past tough stages in the poker game.<br><br>By borer on a boondocks anteroom you possibly can now appearance added advice that's about that play, scout, eurythmie troops, or attack. Of course, these results will rely on appearance of the fights you might be found in.<br><br>It is undoubtedly a helpful component of the diversion as fantastic. When one particular music player has modified, the Conflict of Clan Castle spoils in his or it village, he or she could successfully start or link up with for each faction using diverse gamers exactly where they can take a review with every other and share with troops to just another these troops could be connected either offensively or protectively. The Clash with regards to Clans cheat for without charge additionally holds the greatest district centered globally communicate so gamers could flaunt making use of different players for social bond and as faction enrolling.This recreation is a have to perform on your android device specially if you usually are employing my clash created by clans android hack [http://Www.Answers.com/topic/product product]. |
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| == Design ==
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| [[Image:Ampere balance 1927.jpg|thumb|Precision Ampere balance at the US [[National Bureau of Standards]] (now [[National Institute of Standards and Technology|NIST]]) in 1927. The current coils are visible under the balance, attached to the right balance arm. The Watt balance is a development of the Ampere balance.]]
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| The watt balance is a more accurate version of the [[Ampere balance]], an early [[Electric current|current]] measuring instrument in which the [[force (physics)|force]] between two current-carrying coils of wire is measured and then used to calculate the magnitude of the current. In this new application, the balance will be used in the opposite sense; the current in the coils necessary to support the weight of a standard kilogram mass will be measured, "weighing" the kilogram. The weight of the kilogram is then used to compute the mass of the kilogram by accurately determining the local gravitational acceleration. This will define the mass of a kilogram in terms of a current and a [[voltage]], as described below. Since current and voltage units are defined in terms of fundamental [[physical constant]]s such as the [[speed of light]] and [[Planck's constant]], this will provide an alternative definition of the kilogram in terms of these absolute constants. This may be a better definition than the current one, which defines the kilogram as the mass of a physical artifact, the ''[[international prototype kilogram]]'', which is vulnerable to deterioration or damage.
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| == Origin ==
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| The principle of the watt balance was proposed by B. P. Kibble of the UK [[National Physical Laboratory, UK|National Physical Laboratory]] (NPL) in 1975.<ref>{{citation |last=Kibble |first=B. P. |editor1-last=Sanders |editor1-first=J. H. |editor2-last=Wapstra |editor2-first=A. H. |title=Atomic Masses and Fundamental Constants 5 |pages=545–51 |year=1975 |publisher=Plenum |location=New York}}</ref> The main weakness of the ampere balance method is that the result depends on the accuracy with which the dimensions of the coils are measured. The watt balance method has an extra calibration step in which the effect of the geometry of the coils is eliminated, removing the main source of uncertainty. This extra step involves moving the force coil through a known magnetic flux at a known speed.
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| The watt balance originating from the British National Physical Laboratory was transferred to the [[National Research Council of Canada]] in 2009 and is currently being recommissioned.<ref name="npl.co.uk">[http://www.npl.co.uk/engineering-measurements/mass-force-pressure/mass/research/npl-watt-balance UK National Physical Laboratory: The Watt Balance]</ref> Other watt balance experiments are being undertaken{{When|date=February 2011}} in the US [[National Institute of Standards and Technology]] (NIST), the Swiss [[Federal Office of Metrology]] (METAS) in Berne, the [[International Bureau of Weights and Measures]] (BIPM) near Paris and [[Laboratoire national de métrologie et d’essais]] (LNE) in [[Trappes]], France.<ref>{{CODATA2006}}</ref> As of 2011, the accuracy record is held by the U.S. NIST, with a [[Measurement uncertainty|relative uncertainty]] of 3.6{{e|−8}},<ref name="NIST">{{citation |author=Steiner, R. L.;Williams, E. R.; Liu, R.; Newell, D. B. |title=Uncertainty Improvements of the NIST Electronic Kilogram |year=2007 |journal=IEEE Trans. Instrum. Meas. |volume=56 |issue=2 |pages=592–596 |doi=10.1109/TIM.2007.890590}}</ref> and experiments are continuing towards a goal of 1{{e|−8}}.<ref name="npl.co.uk"/>
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| == Principle ==
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| A conducting wire of length ''L'' which carries an [[electric current]] ''I'' perpendicular to a [[magnetic field]] of strength ''B'' will experience a [[Laplace force]] equal to ''BLI''. In the watt balance, the current is varied so that this force exactly counteracts the [[weight]] of a standard mass ''m'', which is given by the mass multiplied by the local [[gravitational acceleration]] ''g''. This is also the principle behind the ampere balance.
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| Kibble's watt balance avoids the problems of measuring ''B'' and ''L'' with a second calibration step. The same wire (in practice a coil of wire) is moved through the same magnetic field at a known speed ''v''. By [[Faraday's law of induction]], a [[potential difference]] ''U'' is generated across the ends of the wire, which is equal to ''BLv''. Hence the unknown quantities ''B'' and ''L'' can be eliminated from the equations to give
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| :<math>UI = mgv\,</math>
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| Both sides of the equation have the dimensions of [[power (physics)|power]], measured in [[watt]]s in the International System of Units, hence the name "watt balance".
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| == Measurements ==
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| Accurate measurements of electric current and potential difference are made in [[conventional electrical unit]]s (rather than SI units), which are based on fixed "[[conventional electrical unit|conventional value]]s" of the [[Josephson constant]] and the [[von Klitzing constant]], ''K''<sub>J–90</sub> and ''R''<sub>K–90</sub> respectively. The current watt balance experiments are equivalent to measuring the value of the conventional watt in SI units. From the definition of the conventional watt, this is equivalent to measuring the value of the product ''K''<sub>J</sub><sup>2</sup>''R''<sub>K</sub> in SI units instead of its fixed value in conventional electrical units.
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| :<math>K_{\rm J}^2 R_{\rm K} = K_{\rm J-90}^2 R_{\rm K-90}\frac{mgv}{U_{90}I_{90}}</math>
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| The importance of such measurements is that they are also a direct measurement of the [[Planck constant]] ''h'':
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| :<math>h = \frac{4}{K_{\rm J}^2 R_{\rm K}}</math>
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| The principle of the "electronic kilogram" would be to define the value of the Planck constant in the same way that the [[meter]] is defined by the [[speed of light]]. In this case, the electric current and the potential difference would be measured in SI units, and the watt balance would become an instrument to measure mass.
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| :<math>m = \frac{UI}{gv}</math>
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| Any laboratory which had invested the (very considerable) time and money in a working watt balance would be able to measure masses to the same accuracy as they currently measure the Planck constant.
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| In addition to measuring ''UI'', the laboratory must also measure ''v'' and ''g'' using experimental methods that do not depend on the definition of mass. The overall precision of ''m'' depends on the precisions of the measurements of ''U'', ''I'', ''v'' and ''g''. Since there are already methods of measuring ''v'' and ''g'' to very high precision, the uncertainty of the mass measurement is dominated by the measurement of ''UI'', which is the value measured by the watt balance.
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| == References ==
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| {{Reflist}}
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| == External links ==
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| * {{Citation |first1=Richard L. |last1=Steiner |first2=Edwin R. |last2=Williams |first3=David B. |last3=Newell |first4=Ruimin |last4=Liu |title=Towards an electronic kilogram: an improved measurement of the Planck constant and electron mass. |journal=Metrologia |date=October 2005 |volume=42 |issue=5 |pages= 431–441 |doi=10.1088/0026-1394/42/5/014 |url=http://grwavsf.roma1.infn.it/labmec/materiale/met5_5_014.pdf |accessdate=2009-11-17|bibcode = 2005Metro..42..431S }}
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| * [http://nvl.nist.gov/pub/nistpubs/jres/106/4/j64schw.pdf Joshua P. Schwarz, Ruimin Liu, David B. Newell, Richard L. Steiner, Edwin R. Williams, Douglas Smith "Hysteresis and Related Error Mechanisms in the NIST Watt Balance Experiment" (August 2001)]
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| * [http://www.bipm.fr/en/scientific/elec/watt_balance/ Bureau International des Poids et Mesures]
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| * [http://www-optics.unine.ch/former/metrology/Watt_balance/Watt_balance.html Swiss Federal Office of Metrology]
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| {{DEFAULTSORT:Watt Balance}}
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| [[Category:Measuring instruments]]
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