Umov Vector

the vector of the flux density of energy in a physical field; its magnitude is equal to the energy transferred per unit time through unit area surface perpendicular to the direction of energy flux at a given point. The vector is named after N. A. Umov, who, in 1874, was the first to introduce the general concept of energy flux in a continuous medium, based on the law of conservation of energy. The density of the energy flux of an electromagnetic field was determined, based on Maxwell’s equations, by the English physicist J. H. Poynting and is called the Poynting vector.