Tesla (unit)

1 Definition
2 Conversions
3 Examples
4 External links
5 References

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The tesla (symbol T) is the SI derived unit of magnetic field B (which is also known as "magnetic flux density" and "magnetic induction"). One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the Serbian inventor, physicist, and electrical engineer Nikola Tesla. One billionth of a tesla is a nanotesla (nT), equivalent to 0.01 mG (milligauss), and it is in nanoteslas that common metric home measurements are made to determine local magnetic field levels^{[by whom?]}. The strongest fields encountered from permanent magnets are from halbach spheres which can be over 5T^{[citation needed]}.

Definition

This SI unit is named after Nikola Tesla. As with every SI unit whose name is derived from the proper name of a person, the first letter of its symbol is uppercase (T). When an SI unit is spelled out in English, it should always begin with a lowercase letter (tesla), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius" conforms to this rule because the "d" is lowercase.

—Based on The International System of Units, section 5.2.

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 experiences a force of 1 newton, according to the Lorentz force law. As an SI derived unit, the tesla can also be expressed as

$\mathrm{1\, T = 1\,\frac{V\cdot s}{m^2} = 1\,\frac{N}{A\cdot m} = 1\,\frac{Wb}{m^2} = 1\,\frac{kg}{C\cdot s} = 1\,\frac{kg}{A\cdot s^2}}$

(in SI base units).

Units used:

A = ampere

C = coulomb

kg = kilogram

m = metre

N = newton

s = second

T = tesla

V = volt

Wb = weber

Conversions

1 Tesla is equivalent to:

10,000 (or 10⁴) G (gauss), used in the CGS system. Thus, 10 G = 1 mT (millitesla), and 1 G = 10⁻⁴ T.

1,000,000,000 (or 10⁹) γ (gammas), used in geophysics. Thus, 1 γ = 1 nT (nanotesla)

For those concerned with low-frequency 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 (amperes per meter or oersteds) see the article on permeability.

Examples

Main article: Orders of magnitude (magnetic field)

31 µT (3.1×10⁻⁵ T) - strength of Earth's magnetic field at 0° latitude (on the equator)
5 mT - the strength of a typical refrigerator 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 8 T