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Gauss (unit)
The gauss, abbreviated as G or Gs, is the cgs unit of measurement of a magnetic field B, which is also known as the "magnetic flux density" or the "magnetic induction". It is named after German mathematician and physicist Carl Friedrich Gauss. One gauss is defined as one maxwell per square centimeter. The cgs system has been formally superseded by the SI system, which uses the tesla (T) as the unit for B. One gauss equals 1×10^{−4} tesla (100 μT) (1 T=10,000 G).
Unit name and convention
As with all units whose names are derived from a person's name, the first letter of its symbol is uppercase ("G"), but when the unit is spelled out, it should always be written in lowercase ("gauss"), unless it begins a sentence.^{[1]}
Unit conversions
According to the system of Gaussian units (cgs), the gauss is the unit of magnetic flux density B and the equivalent of esu/cm^{2}, while the oersted is the unit of magnetizing field H. One tesla is equal to 10^{4} gauss, and one ampere per meter is equal to 4π × 10^{−3} oersted.^{[2]}
The units for magnetic flux Φ, which is the integral of magnetic field over an area, are the weber (Wb) in the SI and the maxwell (Mx) in the cgs system. The conversion factor is 10^{8}, since flux is the integral of field over an area, area having the units of the square of distance, thus 10^{4} (magnetic field conversion factor) times the square of 10^{2} (linear distance conversion factor, i.e., centimetres per meter).
One gauss is also equal to 10^{−4} kg C^{−1} s^{−1}.
Typical values
- 10^{−9}–10^{−8} gauss – the magnetic field of the human brain
- 0.31–0.58 gauss – the Earth's magnetic field at its surface
- 25 gauss – the Earth's magnetic field in its core^{[3]}
- 50 gauss – a typical refrigerator magnet
- 100 gauss – a small iron magnet
- 2000 gauss – a small neodymium-iron-boron (NIB) magnet
- 600-70,000 gauss – a medical magnetic resonance imaging machine
- 10^{12}–10^{13} gauss – the surface of a neutron star^{[4]}
- 4×10^{13} gauss – the quantum electrodynamic threshold
- 10^{15} gauss – the magnetic field of some newly created magnetars^{[5]}
- 10^{17} gauss – the upper limit to neutron star magnetism^{[5]}
See also
References
- ^ Bureau International des Poids et Mesures (2006). "The International System of Units (SI)" (PDF). 8th ed. Retrieved 2009-05-20.
- ^ Hayt, Jr., William H. (1974). Engineering Electromagnetics, Third Edition. McGraw-Hill. ISBN 0-07-027390-1
- ^ "Medical Daily: First measurement of magnetic field in Earth's core". First measurement of magnetic field in Earth's core. Medical Daily. Retrieved 2010-12-17.
- ^ "How strong are magnets?". Experiments with magnets and our surroundings. Magcraft. Retrieved 2007-12-14.
- ^ ^{a} ^{b} "Magnetars, Soft Gamma Repeaters and Very Strong Magnetic Fields". Robert C. Duncan, University of Texas at Austin. March 2003. Retrieved 2007-05-23.