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 is the zero vector, while the scalar or hemispheric flux density at in every direction in both senses takes the constant scalar value . The reason for the value is that the hemispheric integral is half the full spherical integral, and the integrated effect of the angles of incidence of the radiation on the detector requires a halving of the energy flux according to Lambert's cosine law; the solid angle of a sphere is . The vector definition is suitable for the study of general radiative fields. The scalar or hemispheric spectral flux density is convenient for discussions in terms