A physical experiment concerning the moment of inertia of a rigid disk is described. Basic physical quantities such as the moment of inertia and torque are very important in elementary physics courses. This experiment was designed to improve students' understanding of the relation between the rigid moment of inertia and torque. The moment of inertia about a rigid disk was calculated, and an experimental method was developed for determining the torque on the basis of magneto-electrical measurements of the rigid angular acceleration. In the experimental setup, a spur gear was used as a rigid disk. We developed a method for measuring the torque of an electrical motor via a magnetic induction method using a spur gear, SmCo permanent magnet and pickup coil.