Magnetic field 'magnetic field' is used to describe as well as or in place of . There are many alternative names for both (see sidebar). In SI units, is measured in teslas (symbol: T) and correspondingly (magnetic flux) is measured in webers (symbol: Wb) so that a flux density of 1 Wb/m is 1 tesla. The SI unit of tesla is equivalent to (newton·second)/(coulomb·metre). In Gaussian-cgs units, is measured in gauss (symbol: G). (The conversion is 1 T = 10000 G.) One nanotesla is equivalent to 1 gamma (symbol: γ). The -field is measured in amperes per metre (A/m) in SI units,
Magnetic tension force as the divergence of the Maxwell tensor: which gives the electromagnetic force density in terms of Maxwell stress tensor, formula_24, and the Poynting vector, formula_25. Now, the magnetic tension is implicitly included inside formula_24. The implication of the above relation is the conservation of momentum. Here, formula_27 is the momentum flux density and plays a role similar to formula_28 in Poynting's theorem. Magnetic tension force The magnetic tension force is a restoring force (SI unit: Pa·m) that acts to straighten bent magnetic field lines. It equals: It is analogous to rubber bands and their restoring force. The force is directed