  The study of quasi-periodic oscillations (QPOs) of X-ray flux observed in
many microquasars can provide a powerful tool for testing of the phenomena
occurring in strong gravity regime. QPOs phenomena can be well related to the
oscillations of charged particles in accretion disks orbiting Kerr black holes
immersed in external large-scale magnetic fields. In the present paper we study
the model of magnetic relativistic precession and provide estimations of the
mass and spin of the central object of the microquasar H~1743-322 which is a
candidate for a black hole. Moreover, we discuss the possible values of
external magnetic field and study its influence on the motion of charged
particles around rotating black hole.
