初中物理第二册中,演示通电螺线管磁性强弱的实验效果很不理想,难以成功。该实验难以成功的关键有二。(1)选用弹簧作为磁性强弱的指示器不合适。从理论上来说,由弹簧的伸缩来表征挂在弹簧下面的铁块所受磁力的大小,从而说明通电螺线管磁性的强弱,是完全正确的。问题是,在实际操 In the second volume of junior high school physics, the experimental results demonstrating the magnetic strength of the energized solenoids are not ideal and are difficult to succeed. The key to the success of this experiment is twofold. (1) The use of a spring as an indicator of magnetic strength is inappropriate. Theoretically speaking, the size of the magnetic force of the iron block hung under the spring is characterized by the expansion and contraction of the spring, thus indicating that the magnetic strength of the energized solenoid is completely correct. The problem is that in practice