The director dynamics for a low molar mass nematic liquid crystal (LC) has been investigated theoretically based on the hydrodynamic theory including the director motion. Analysis of the numerical results for the turn-on process provides an evidence for the appearance of the spatially periodic patterns in 4-n-pentyl-4'-cyanobiphenyl LC film, only in response to the suddenly applied strong electric field orthogonal to the magnetic field. It has been shown that at the values of the voltage in 200 V across the 194.7 mu m LC film and the magnetic field of 7.05 T directed at the angle alpha = 1.57(similar to 89.99 degrees) between two fields there is the threshold value of the amplitude of the thermal fluctuations of the director over the LC sample which provide the nonuniform rotation mode rather than the uniform one, whereas the lower values both of the amplitude and the angle alpha (<1.565(similar to 88.81 degrees)) dominate the uniform mode. During the turn-off process, the reorientation of the director to its equilibrium orientation is characterized by the complex destroying of the initially periodic structure to a monodomain state. (C) 2013 Elsevier B.V. All rights reserved.