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《物理教师》1993年第5期中的《谈“四自”教育教学法在物理教学中的应用》一文中介绍了这样一种现象:把收音机放在一个铁盘上,再用金属罩罩住,收音机的声音立即减弱.原丈中是把这一现象作为静电屏蔽的证据加以演示的.笔者认为这种做法不妥. 电场中的导体能够出现静电平衡,必须是静电场.静电屏蔽亦应是对静电场的“屏蔽”.收音机接收的电磁波是高频变化的电磁场.电磁波在空间中传播遇到导体,涉及到的是电磁波由一种媒质(空气)接触到另一种媒质(金属导体)的表面,将同时发生的是反射和折射两种物理现象.由电动力学知识可知:
The article “On the application of the “four-self” education and pedagogy in physics teaching” in the 5th issue of “Physics Teachers” in 1993 introduced a phenomenon in which the radio is placed on an iron plate and covered with a metal cover. The sound of the radio immediately weakened. The former Zhang Zhong demonstrated this phenomenon as evidence of electrostatic shielding. The author believes that this approach is inappropriate. The conductors in the electric field can be electrostatically balanced and must be electrostatic fields. Electrostatic shielding should also be used. It is the “shield” of the electrostatic field. The radio waves received by the radio are electromagnetic fields that change at high frequency. Electromagnetic waves travel in space and encounter conductors. It is related to electromagnetic waves that contact from one medium (air) to another (metal conductors). On the surface of the surface, both physical phenomena of reflection and refraction will occur at the same time. It can be known from the knowledge of electrodynamics: