abampere or biot
Unit systemCGS-EMU
Unit ofelectric current
SymbolabA or Bi
Named afterA.-M. Ampère or J.-B. Biot
In CGS base unitsg1/2⋅cm1/2⋅s−1 [1]:25
1 abA in ...... corresponds to ...
SI base units10 amperes[1]:25
CGS-ESUccgs statamperes[Note 1]2.9979×1010 statamperes[2]:16

The abampere (abA), also called the biot (Bi) after Jean-Baptiste Biot, is the derived electromagnetic unit of electric current in the emu-cgs system of units (electromagnetic cgs). One abampere corresponds to ten amperes in the SI system of units. An abampere of current in a circular path of one centimeter radius produces a magnetic field of 2π oersteds at the center of the circle.

The name abampere was introduced by Kennelly in 1903 as a short name for the long name (absolute) electromagnetic cgs unit of current that was in use since the adoption of the cgs system in 1875.[3] The abampere was coherent with the emu-cgs system, in contrast to the ampere, the practical unit of current that had been adopted too in 1875.

The emu-cgs (or "electromagnetic cgs") units are one of several systems of electromagnetic units within the centimetre–gram–second system of units; others include esu-cgs, Gaussian units, and Lorentz–Heaviside units. In these other systems, the abampere is not one of the units; the "statcoulomb per second" or statampere is used instead.

The other units in this system related to the abampere are:


  1. ^ The dimensionless constant ccgs = 2.99792458×1010 is numerically equal to the magnitude of the speed of light when the latter is expressed in cm/s.


  1. ^ a b Gyllenbok, Jan (2018). Encyclopaedia of Historical Metrology, Weights, and Measures: Volume 1. Birkhäuser. ISBN 978-3-319-57598-8.
  2. ^ Cook, James L. (1991). Conversion Factors. Oxford University Press. ISBN 978-0-19-856349-5.
  3. ^ A.E. Kennelly (1903) "Magnetic units and other subjects that might occupy attention at the next international electrical congress" 20th Annual Convention of the American Institute of Electrical Engineers, 1903