The calculation of the power losses in a ferromagnetic is often executed with the utilisation of analytic dependence. This dependence was marked on the basis of the Maxwell equations. So, it accepts the ferromagnetic material as devoid of the magnetic domains. The domains behaviour in external magnetic field is imitated with help of the magnetic permeability. However, when in a real ferromagnetic two field harmonics coexists (the fundamental harmonic which establish the magnetic work conditions and the higher order harmonic with small amplitude), the computed power loss values can be unreal. The authors of this paper show the dependence of the power losses (the power losses caused by higher order harmonic) in relation with the temporary shape of the wall (the temporary shape is connected with the temporary value of the fundamental harmonic field integrated over a cross section).