tesla

SI coherent derived unit with special name and symbol

Name	Symbol	Quantity	Base units
tesla	T	magnetic flux density	kg s⁻² A^-1
The tesla, symbol T, is the SI coherent derived unit of magnetic flux density, and of magnetic field strength. It is the special name for the kg s⁻² A^-1. One tesla is equal to a magnetic flux density of one weber per square metre.
Definition			h c^-2 Δν_Cs² e^-1
$1 \mspace{4mu} \text{T} \mspace{6mu} = \dfrac{(299 \mspace{4mu} 792 \mspace{4mu} 458)^2(1.602 \mspace{4mu} 176 \mspace{4mu} 634 \times 10^{-19})}{(6.626 \mspace{4mu} 070 \mspace{4mu} 15 \times 10^{-34})(9 \mspace{4mu} 192 \mspace{4mu} 631 \mspace{4mu} 770)^2} \mspace{6mu} \dfrac{h \mspace{4mu} {\Delta \nu _{Cs}}^2}{c^2 \mspace{4mu} e}\\ \\ \\ 1 \mspace{4mu} \text{T} \mspace{6mu} \approx 2.571 \mspace{4mu} 674 \mspace{4mu} 759 \mspace{4mu} 493 \mspace{4mu} 629 \mspace{4mu} 589 \times10^{11} \mspace{6mu} h \mspace{4mu} c^{-2} \mspace{4mu} {\Delta \nu _{Cs}}^2 \mspace{4mu} e^{-1}$

The tesla is named after the Serbian-American electrical engineer Nikola Tesla.

Magnetic flux density

A magnetic field is a vector field that describes the magnetic influence of electric currents and magnetised materials. Magnetic fields are created by magnetised material and by moving electric charges (electric currents) such as those used in electromagnets.

When a magnetic field is applied to a material, the resulting magnetic flux density, B, is directly proportional to the strength of the applied magnetic field, H, and the magnetic permeability, μ, of the material.

Using SI coherent units,

$\mathbf{B} = \mu \mspace{2mu} \mathbf{H}$

where:

B is the magnetic flux density in teslas, symbol T, (or webers per square metre, symbol Wb m^-2),
H is the strength of the applied magnetic field in amperes per metre, symbol A m^-1,
μ is the magnetic permeability in henries per metre, symbol H m^-1.

Lorentz force

A particle, carrying a charge of one coulomb, and moving perpendicularly through a magnetic field of one tesla, at a speed of one metre per second, experiences a force of magnitude one newton.

Measurement

The finest precision for a magnetic field measurement was attained by Gravity Probe B at 5 aT (5×10⁻¹⁸ T).

Magnetometers are devices used to measure the local magnetic field.

Important classes of magnetometers include using induction magnetometer (or search-coil magnetometer) which measure only varying magnetic fields, rotating coil magnetometer, Hall effect magnetometers, NMR magnetometers, SQUID magnetometers, and fluxgate magnetometers.

The magnetic fields of distant astronomical objects are measured through their effects on local charged particles. For instance, electrons spiraling around a field line produce synchrotron radiation that is detectable in radio waves.