关键词: 电动机, 滑动接触, 角加速度, 指数衰减

Abstract: Attaching a strong light magnet to the head of a steel screw,the screw can hang frorn the terminal of a battery.Completing the circuit by a sliding contact on the magnet causes the screw to rotate.We investigate the parameters determining the angular velocity of the screw theoretically and experimentally and show the theoretical solution,experimental results and the verifications of the phenomena.The conclusion is that the angular velocity of the screw and the pill increases at the beginning of the process and then approaches a constant value.The crucial effects that influence the angular velocity include the induction electromotive force and the moment of resistance that grows with the angular velocity, which is determined by the magnetic flux in the magnet,the current in the circuit,the rotational inertia of the magnetic pill and the moment of resistance.

Key words: electromotor, sliding contact, angular acceleration, exponential characteristic