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Though the Josephson effect is still used to realize a volt, the constant used has changed slightly. For the Josephson constant, K J = 2e/h (where e is the elementary charge and h is the Planck constant), a "conventional" value K J-90 = 0.483 5979 GHz/μV was used for the purpose of defining the volt.
One joule is also equivalent to any of the following: [6] The work required to move an electric charge of one coulomb through an electrical potential difference of one volt, or one coulomb-volt (C⋅V). This relationship can be used to define the volt.
Voltage, also known as (electrical) potential difference, electric pressure, or electric tension is the difference in electric potential between two points. [ 1 ] [ 2 ] In a static electric field , it corresponds to the work needed per unit of charge to move a positive test charge from the first point to the second point.
Log-base-10 of the ratios between various measures of energy. The table illustrates the wide range of magnitudes among conventional units of energy. For example, 1 BTU is equivalent to about 1,000 joules, and there are 25 orders-of-magnitude difference between a kilowatt-hour and an electron-volt.
It is usually measured in volts, and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity. [ 25 ] : 494–98 This definition of potential, while formal, has little practical application, and a more useful concept is that of electric potential difference , and is the energy ...
An electronvolt is the amount of energy gained or lost by a single electron when it moves through an electric potential difference of one volt. Hence, it has a value of one volt, which is 1 J/C, multiplied by the elementary charge e = 1.602 176 634 × 10 −19 C. [2] Therefore, one electronvolt is equal to 1.602 176 634 × 10 −19 J. [1]
When a voltmeter is connected between two different types of metal, it measures the potential difference corrected for the different atomic environments. [6] The quantity measured by a voltmeter is called electrochemical potential or fermi level , while the pure unadjusted electric potential, V , is sometimes called the Galvani potential , ϕ .
The SI unit of electric potential energy is joule (named after the English physicist James Prescott Joule). In the CGS system the erg is the unit of energy, being equal to 10 −7 Joules. Also electronvolts may be used, 1 eV = 1.602×10 −19 Joules.