  It is shown that the generally accepted definition of the Poynting vector and
the energy flux vector defined by means of the energy density of the
electromagnetic field (Umov vector) lead to the prediction of the different
results touching electromagnetic energy flux. The experiment shows that within
the framework of the mentioned generally accepted definitions the Poynting
vector adequately describes the electromagnetic energy flux unlike the Umov
vector. Therefore one can conclude that a generally accepted definitions of the
electromagnetic energy density and the Poynting vector, in general, are not
always compatible.
