PURPOSE: To measure an angular acceleration, etc. by using a theory that an induction voltage is induced in a coil, when an angular velocity of an electric conductor rotating at a high speed is varied.

CONSTITUTION: When an electric conductor rod 1 is rotated 2 at a high speed, a magnetic field 3 passing through the electric conductor rod 1 is generated. When an angular velocity W of the high speed rotation 2 is constant, the magnetic field 3 passing through a coil 4 is constant, but when the angular velocity W is varied, the magnetic field 3 passing through the coil 4 is varied, an induction current flows to the coil 4, and a galvanometer 5 is deflected. In case the electric conductor 1 is a ferromagnetic material, a relation of an angular velocity and magnetization is not linear, but when a ferromagnetic material rod is used, an induction voltage induced by a variation of the angular velocity W is larger than that of other electric conductor rod. Also, even when the angular velocity W of the electric conductor 1 is made constant and the electric conductor 1 is moved in the vicinity of the coil 4, the magnetic field 3 is varied, therefore, the galvanometer 5 is deflected.