Abstract
We measured induced electromotive force quantitatively using a galvanometer while a magnet pass through a coil. This measurement has errors usually because of a slow response of a galvanometer for induced electromotive force. Therefore it is necessary to improve the response and reduce the change rate of the force. Then we inserted an external registor (critical damping resistor) in a measurement circuit and moved a magnet slowly using a DC motor. As a result, we obtained the experimental conditions that the resistor was about 140 ohm and the velocity of the magnet was under 5cm/s. In these conditions, the induced electromotive force was proportional to the time derivative of magnetic flux.
