Gauss (unit)

The gauss, abbreviated as G, is the cgs unit of measurement of a magnetic field B (which is also known as the "magnetic flux density", or the "magnetic induction"), named after the German mathematician and physicist Carl Friedrich Gauss. One gauss is defined as one maxwell per square centimeter; it equals 1×10⁻⁴ tesla. Because the tesla is so large in regards to everyday usage, it is common to see the strength of magnets reported in gauss.

Unit name and convention

This unit is named after Carl Friedrich Gauss. As with all units whose names are derived from the proper name of a person, 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]

Units conversions

According to the centimeter gram second system of units (cgs), the gauss is the unit of magnetic field B, while the oersted is the unit of magnetizing field H. One tesla is equal to 10⁴ 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 10⁸, since flux is the integral of field over an area, area having the units of the square of distance, thus 10⁴ (magnetic field conversion factor) times the square of 10² (linear distance conversion factor, i.e., centimetres per meter).

Another unit conversion that may be useful is 1 gauss = 10⁻⁴ kg C⁻¹ s⁻¹.

Typical values

Main article: Orders of magnitude (magnetic field)

• 10⁻⁹–10⁻⁸ gauss: the human brain magnetic field
• 0.31–0.58 gauss: the Earth's magnetic field on 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
• 15,000-30,000 gauss: a medical magnetic resonance imaging electromagnet
• 10¹²–10¹³ gauss: the surface of a neutron star^[4]
• 4×10¹³ gauss: the quantum electrodynamic threshold
• 10¹⁵ gauss: the magnetic field of some newly created magnetars^[5]
• 10¹⁷ gauss: the upper limit to neutron star magnetism, no known object in the universe can generate a stronger magnetic field^[5]

See also

• Centimetre gram second system of units
• Gaussian units
• Carl Friedrich Gauss
• Magnetic field

References

1. ^ Bureau International des Poids et Mesures (2006). The International System of Units (SI). 8th ed.. http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf. Retrieved 2009-05-20. 
2. ^ Hayt, Jr., William H. (1974). Engineering Electromagnetics, Third Edition. McGraw-Hill. ISBN 0-07-027390-1
3. ^ "Medical Daily: First measurement of magnetic field in Earth's core". First measurement of magnetic field in Earth's core. Medical Daily. http://www.medicaldaily.com/news/20101217/4716/first-measurement-of-magnetic-field-in-earths-core.htm. Retrieved 2010-12-17. 
4. ^ "How strong are magnets?". Experiments with magnets and our surroundings. Magcraft. http://www.coolmagnetman.com/magflux.htm. Retrieved 2007-12-14. 
5. ^ ^{a b} "Magnetars, Soft Gamma Repeaters and Very Strong Magnetic Fields". Robert C. Duncan, University of Texas at Austin. March 2003. http://solomon.as.utexas.edu/~duncan/magnetar.html#Epilog. Retrieved 2007-05-23.