Holm device is a solid -state electronic device that uses the Hall effect. E.H. Hall discovered in 1879: A rectangular conductor or semiconductor material in the magnetic field with a magnetic induction intensity of BZ, in the direction of the magnetic field, the current IX passes the test piece, in the direction of both perpendicular to the magnetic field BZ and vertically in the current IX It will generate electric field EY, this is the Hall effect. This electric field generates an electric momentum between the electrode 3 and 4, called Hall's electromotive force.