Magnetic moment and external fields is not part of this internal energy. The unit for magnetic moment in terms of the International System of Units (SI) base units is A⋅m, where A is the ampere (the SI unit of current) and m is the meter (the SI unit of distance). This has equivalents in other units used in SI including: where N is the newton (the SI unit of force), T is the tesla (the SI unit of magnetic flux density), and J is the joule (the SI unit of energy). In the CGS system, there are several different sets of electromagnetism
Spectral flux density As described below, if the direction of the flux density vector is known in advance because of a symmetry, namely that the radiative field is uniformly layered and flat, then the vector flux density can be measured as the 'net flux', by algebraic summation of two oppositely sensed scalar readings in the known direction, perpendicular to the layers. At a given point in space, in a steady-state field, the vector flux density, a radiometric quantity, is equal to the time-averaged Poynting vector, an electromagnetic field quantity. Within the vector approach to the definition, however, there are several specialized sub-definitions. Sometimes