Ampere (unit)

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The ampere, symbol A, is the SI unit of electric current. It is defined by application of Ampere's equation:

 \frac{F}{l} = \frac{\mu_0\,i^2}{2\pi r}.

One ampere is that constant current i which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed r = 1 metre apart in vacuum, would produce between these conductors a force F equal to 2 x 10-7 newton per meter of length l.[1] This sets the value of the magnetic constant μ0 to 4π x 10−7 N/A2.

The ampere is named for André-Marie Ampère, an early investigator of electricity, magnetism, and chemistry.

The ampere has undergone a number of redefinitions; the current standard was adopted in 1948. One definition adopted legally before the current SI definition was "that unvarying current that would deposit 0.001 118 000 grams of silver per second from a solution of silver nitrate in water". This earlier definition is approximately 0.99985 A (SI).

[edit] Related units

The SI uses the ampere as its basic unit of electrical measure; all other units are derived from the ampere.

A=C\cdot s^{-1}=\frac{C}{s}
 A = m^2 \cdot  kg \cdot s^{-3} \cdot V^{-1} = \frac{ m^2 \cdot kg}{s^{3} \cdot V}.
A=V\cdot \Omega^{-1}=\frac{V}{\Omega} = \sqrt{m^2 \cdot kg \cdot s^{-3}\, \Omega^{-1}}

[edit] Sources

[edit] References

  1. International Bureau of Weights and Measures From the website of the International Bureau of Weights and Measures.
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