Tesla (unit)

The tesla (symbol T) is the SI unit used to measure the strength of magnetic fields. Tesla can be measured in different ways; for example, one tesla is equal to one weber per square meter.

The tesla was first defined in 1960 by the General Conference on Weights and Measures (CGPM).^[1] It was named in honor of the physicist, electrical engineer, and inventor, Nikola Tesla.

Definitions

Using only the seven base SI units, the definition of a tesla is:

${\displaystyle {\mbox{T}}={\dfrac {\mbox{kg}}{{\mbox{A}}\cdot {\mbox{s}}^{2}}}}$

Using other SI derived units, a tesla is also equal to:

${\displaystyle {\mbox{T}}={\dfrac {{\mbox{V}}\cdot {\mbox{s}}}{{\mbox{m}}^{2}}}={\dfrac {\mbox{N}}{{\mbox{A}}\cdot {\mbox{m}}}}={\dfrac {\mbox{Wb}}{{\mbox{m}}^{2}}}={\dfrac {\mbox{kg}}{{\mbox{C}}\cdot {\mbox{s}}}}={\dfrac {{\mbox{N}}\cdot {\mbox{s}}}{{\mbox{C}}\cdot {\mbox{m}}}}}$

The units used are:

A = ampere
C = coulomb
kg = kilogram
m = meter
N = newton
s = second
T = tesla
V = volt
Wb = weber

A tesla is also equal to 10,000 (10⁴) gauss in the CGS system of units.

Example values

• 3.1×10⁻⁵–5.8^-5 T – the Earth's magnetic field at its surface
• 5×10^-3 T – the strength of a typical refrigerator magnet
• 0.3 T – the strength of solar sunspots
• 1.25T – the strength of the surface of a neodymium magnet
• 1.5−3 T – strength of medical magnetic resonance imaging systems
• 4 T – strength of the superconducting magnet built around the CMS detector at CERN^[2]
• 13 T – strength of ITER fusion reactor^[3]
• 16 T – magnetic field strength required to levitate a frog as part of an Ig Nobel Prize winning project.^[4]