Tesla (unit) One tesla is equivalent to: One tesla is equal to 1 V·s/m. This can be shown by starting with the speed of light in vacuum, "c" = (εμ), and inserting the SI values and units for "c" (), the vacuum permittivity ε (), and the vacuum permeability μ (). Cancellation of numbers and units then produces this relation. For the relation to the units of the magnetising field (ampere per metre or Oersted), see the article on permeability. Tesla (unit) The tesla (symbol T) is a derived unit of the magnetic field strength (also, magnetic flux density) in the International
Magnetic helicity it (gauge transformation). However, for perfectly conducting boundaries or periodic systems without a net magnetic flux, the magnetic helicity is gauge invariant. A gauge-invariant "relative helicity" has been defined for volumes with non-zero magnetic flux on their boundary surfaces. If the magnetic field is turbulent and weakly inhomogeneous a magnetic helicity "density" and its associated flux can be defined in terms of the density of field line linkages. Magnetic helicity The helicity of a smooth vector field defined on a domain in 3D space is the standard measure of the extent to which the field lines wrap and coil around