在所有有运动发生的电机、电器和仪器当中,除了少数是由于静电的吸力或斥力的作用而外,大都是因了电磁的作用才产生运动的。电磁铁的最大优点便是它的磁性能产生、消除或者有强度的变化,它的运动可以准确地受到控制,通常还是在很远很远的处所来控制其中的电流的。世界上最大的和最小的,以及最精致的磁铁都是电磁铁,其中有的有铁质有的没有铁质。所有 Of all motors, electrical appliances and instruments that have motions, except for a few that are due to electrostatic suction or repulsion, most of them are due to electromagnetic action. The biggest advantage of an electromagnet is that its magnetic properties are generated, eliminated or changed in intensity. Its motion can be accurately controlled, and currents are usually controlled at far and distant locations. The largest and smallest magnets in the world, as well as the most elaborate magnets, are electromagnets, some of which are iron-free and not iron. all