只要穿过闭合电路的磁通量发生变化,闭合电路中就有感应电流产生.是否产生感应电动势与磁通量的变化率ΔΔ/φt相关.即E=NΔΔ/φt,常见的表达式: As long as the magnetic flux passing through the closed circuit changes, there is an induced current in the closed circuit. Whether the induced electromotive force is generated depends on the rate of change of magnetic flux ΔΔ / φt, that is, E = NΔΔ / φt, and the common expression: