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Tesla (unit)
Tesla  

300px The tesla definition T = Wb/m^{2} is prominently depicted on the 100 Serbian dinars banknote, along with the picture of Nikola Tesla.  
Unit information  
Unit system  SI derived unit 
Unit of  Magnetic flux density 
Symbol  T 
Named after  Nikola Tesla 
In SI base units:  1 T = 1 kg·s^{−2}·A^{−1} 
The tesla (symbol T) is the SI derived unit of magnetic flux density, commonly denoted as B. One tesla is equal to one weber per square metre, and it was named in 1960^{[1]} in honour of Nikola Tesla. The strongest fields encountered from permanent magnets are from Halbach spheres which can be over 4.5 T. The strongest field trapped in a superconductor in a lab as of July 2014 is 17.6 T.^{[2]} The record magnetic field has been produced by scientists at the Los Alamos National Laboratory campus of the National High Magnetic Field Laboratory, the world's first 100 Tesla nondestructive magnetic field.^{[3]}
The unit was announced during the Conférence Générale des Poids et Mesures in 1960.
Contents
Definition
A particle carrying a charge of 1 coulomb and passing through a magnetic field of 1 tesla at a speed of 1 meter per second perpendicular to said field experiences a force with magnitude 1 newton, according to the Lorentz force law. As an SI derived unit, the tesla can also be expressed as
 <math> \mathrm{T}
= \dfrac{\mathrm{V}\cdot{\mathrm{s}}}{\mathrm{m}^2} = \dfrac{\mathrm{N}}{\mathrm{A}{\cdot}\mathrm{m}} = \dfrac{\mathrm{J}}{\mathrm{A}{\cdot}\mathrm{m}^2} = \dfrac{\mathrm{H}{\cdot}\mathrm{A}}{\mathrm{m}^2} = \dfrac{\mathrm{Wb}}{\mathrm{m}^2} = \dfrac{\mathrm{kg}}{\mathrm{C}{\cdot}\mathrm{s}} = \dfrac{\mathrm{N}{\cdot}\mathrm{s}}{\mathrm{C}{\cdot}\mathrm{m}} = \dfrac{\mathrm{kg}}{\mathrm{A}{\cdot}\mathrm{s}^2} </math>
(The last equivalent is in SI base units).^{[4]}
Units used:
 A = ampere
 C = coulomb
 kg = kilogram
 m = meter
 N = newton
 s = second
 H = henry
 T = tesla
 V = volt
 J = joule
 Wb = weber
Electric vs. magnetic field
In the production of the Lorentz force, the difference between these types of field is that a force from a magnetic field on a charged particle is generally due to the charged particle's movement^{[5]} while the force imparted by an electric field on a charged particle is not due to the charged particle's movement. This may be appreciated by looking at the units for each. The unit of electric field in the MKS system of units is newtons per coulomb, N/C, while the magnetic field (in teslas) can be written as N/(C·m/s). The dividing factor between the two types of field is meters/second (m/s), which is velocity. This relationship immediately highlights the fact that whether a static electromagnetic field is seen as purely magnetic, or purely electric, or some combination of these, is dependent upon one's reference frame (that is: one's velocity relative to the field).^{[6]}^{[7]}
In ferromagnets, the movement creating the magnetic field is the electron spin^{[8]} (and to a lesser extent electron orbital angular momentum). In a currentcarrying wire (electromagnets) the movement is due to electrons moving through the wire (whether the wire is straight or circular).
Conversions
1 tesla is equivalent to:^{[9]}
 10,000 (or 10^{4}) G (gauss), used in the CGS system. Thus, 10 kG = 1 T (tesla), and 1 G = 10^{−4} T.
 1,000,000,000 (or 10^{9}) γ (gamma), used in geophysics.^{[10]} Thus, 1 γ = 1 nT (nanotesla).
 42.6 MHz of the ^{1}H nucleus frequency, in NMR. Thus a 1 GHz NMR magnetic field is 23.5 tesla.
For those concerned with lowfrequency electromagnetic radiation in the home, the following conversions are needed most:
 1000 nT (nanotesla) = 1 µT (microtesla) = 10 mG (milligauss)
 1,000,000 µT = 1 T
For the relation to the units of the magnetizing field (ampere per meter or oersted) see the article on permeability.
Examples
 31.869 µT (3.2 × 10^{−5} T) – strength of Earth's magnetic field at 0° latitude, 0° longitude
 5 mT – the strength of a typical refrigerator magnet
 0.3 T – the strength of solar sunspots
 1.25 T – magnetic field intensity at the surface of a neodymium magnet
 1 T to 2.4 T – coil gap of a typical loudspeaker magnet
 1.5 T to 3 T – strength of medical magnetic resonance imaging systems in practice, experimentally up to 17 T^{[11]}
 4 T – strength of the superconducting magnet built around the CMS detector at CERN^{[12]}
 8 T – the strength of LHC magnets.
 11.75 T – the strength of INUMAC magnets, largest MRI scanner.^{[13]}
 13 T – strength of the superconducting ITER magnet system^{[14]}
 16 T – magnetic field strength required to levitate a frog^{[15]} (via diamagnetic levitation of the water in its body tissues) according to the 2000 Ig Nobel Prize in Physics.^{[16]}
 17.6 T – strongest field trapped in superconductor in lab as of July 2014^{[17]}
 1020 T – maximum field strengths of superconducting electromagnets at cryogenic temperatures
 33.8 T – the current (2009) record of superconducting electromagnets ^{[18]}
 10^{8}10^{11} T (100 MT100 GT) – magnetic strength of the average magnetar
Notes and references
 ^ "Details of SI units". sizes.com. 20110701. Retrieved 20111004.
 ^ http://www.magnet.fsu.edu/mediacenter/factsheets/records.html
 ^ "Strongest nondestructive magnetic field: world record set at 100tesla level". https://www.lanl.gov. Los Alamos National Laboratory. Retrieved 6 November 2014.
 ^ The International System of Units (SI), 8th edition, BIPM, eds. (2006), ISBN 9282222136, Table 3. Coherent derived units in the SI with special names and symbols
 ^ Gregory, Frederick (2003). History of Science 1700 to Present. The Teaching Company.
 ^ Parker, Eugene (2007). Conversations on electric and magnetic fields in the cosmos. Princeton University press. p. 65.
 ^ Kurt, Oughstun (2006). Electromagnetic and optical pulse propagation. Springer. p. 81.
 ^ Herman, Stephen (2003). Delmar's standard textbook of electricity. Delmar Publishers. p. 97.
 ^ McGraw Hill Encyclopaedia of Physics (2nd Edition), C.B. Parker, 1994, ISBN 0070514003
 ^ "Geomagnetism Frequently Asked Questions". National Geophysical Data Center. Retrieved 21 October 2013.
 ^ "UltraHigh Field". Bruker BioSpin. Retrieved 20111004.
 ^ "Superconducting Magnet in CMS". Retrieved 9 February 2013.
 ^ "ISEULT  INUMAC". Retrieved 17 February 2014.
 ^ "ITER – the way to new energy". Retrieved 20120419.
 ^ "Of Flying Frogs and Levitrons" by M.V. Berry and A.K. Geim, European Journal of Physics, v. 18, 1997, p. 307–13.". Retrieved 12 May 2013.
 ^ "The 2000 Ig Nobel Prize Winners". Retrieved 12 May 2013.
 ^ "Superconductor Traps The Strongest Magnetic Field Yet". Retrieved 2 July 2014.
 ^ "Mag Lab World Records". Media Center. National High Magnetic Field Laboratory, USA. 2008. Retrieved 20080831.
External links
40x40px  Look up tesla in Wiktionary, the free dictionary. 
