# Physics:Gauss (unit)

Short description: Unit of magnetic induction
gauss
Unit systemGaussian and emu-cgs
Unit ofmagnetic flux density (also known as magnetic induction, or the B-field, or magnetic field)
SymbolG or Gs
Named afterCarl Friedrich Gauss
Conversions
1 G or Gs in ...... is equal to ...
SI derived units   10−4 tesla[lower-alpha 1]
Gaussian base units   1 cm−1/2g1/2s−1
esu-cgs   1/ccgs esu[lower-alpha 2]

The gauss, symbol G (sometimes Gs), is a unit of measurement of magnetic induction, also known as magnetic flux density. The unit is part of the Gaussian system of units, which inherited it from the older CGS-EMU system. It was named after the German mathematician and physicist Carl Friedrich Gauss in 1936. One gauss is defined as one maxwell per square centimetre.

As the cgs system has been superseded by the International System of Units (SI), the use of the gauss has been deprecated by the standards bodies, but is still regularly used in various subfields of science. The SI unit for magnetic flux density is the tesla (symbol T),[1] which corresponds to 10,000gauss.

## Name, symbol, and metric prefixes

Albeit not a component of the International System of Units, the usage of the gauss generally follows the rules for SI units. Since the name is derived from a person's name, its symbol is the uppercase letter G. When the unit is spelled out, it is written in lowercase ("gauss"), unless it begins a sentence.[2]:147–148 The gauss may be combined with metric prefixes,[3]:128 such as in milligauss, mG (or mGs), or kilogauss, kGauss or kG.

## Unit conversions

\displaystyle{ \begin{align} 1\,{\rm G} &= {\rm Mx}{\cdot}{\rm cm}^{-2} = \frac{\rm g}{{\rm Bi}{\cdot}{\rm s}^2}\\ &\text{ ≘ } 10^{-4}\,{\rm T} = 10^{-4}\frac{\rm kg}{{\rm A}{\cdot}{\rm s^2}} \end{align} }

The gauss is the unit of magnetic flux density B in the system of Gaussian units and is equal to Mx/cm2 or g/Bi/s2, while the oersted is the unit of H-field. One tesla (T) corresponds to 104 gauss, and one ampere (A) per metre corresponds to 4π × 10−3 oersted.

The units for magnetic flux Φ, which is the integral of magnetic B-field over an area, are the weber (Wb) in the SI and the maxwell (Mx) in the CGS-Gaussian system. The conversion factor is 108 maxwell per weber, since flux is the integral of field over an area, area having the units of the square of distance, thus 104 G/T (magnetic field conversion factor) times the square of 102 cm/m (linear distance conversion factor). 108 Mx/Wb = 104 G/T × (102 cm/m)2.

## Typical values

Main page: Physics:Orders of magnitude (magnetic field)

## Notes

1. The electromagnetic Gaussian and SI quantities correspond (symbol '≘') rather than being equal (symbol '=').
2. ccgs = 2.99792458×1010 is the numeric part of the speed of light when expressed in cgs units.

## References

1. NIST Special Publication 1038, Section 4.3.1
2. Buffett, Bruce A. (2010), "Tidal dissipation and the strength of the Earth's internal magnetic field", Nature, volume 468, pages 952–954, doi:10.1038/nature09643
3. Hoadley, Rick. "How strong are magnets?".
4. Pyrhönen, Juha; Jokinen, Tapani; Hrabovcová, Valéria (2009). Design of Rotating Electrical Machines. John Wiley and Sons. p. 232. ISBN 978-0-470-69516-6.
5. Laughton, Michael A.; Warne, Douglas F., eds (2003). "8". Electrical Engineer's Reference Book (Sixteenth ed.). Newnes. ISBN 0-7506-4637-3.
6. "How strong are magnets?". Experiments with magnets and our surroundings. Magcraft.
7. Duncan, Robert C. (March 2003). "Magnetars, Soft Gamma Repeaters and Very Strong Magnetic Fields". University of Texas at Austin.