极化电荷与自由电荷之间区别的演示实验

通过将导体放入静电场发生的静电感应现象和将绝缘体（电介质）放入静电场发生的极化现象，演示一组实验，生动地显示了电介质被极化出的正、负电荷，既不能离开电介质，也不能在电介质中自由移动，就是将带有极化电荷的电介质与导体接触，极化电荷也不会与导体上的自由电荷中和，即极化电荷牢固地束缚在介质上．说明极化电荷与自由电荷之间的本质区别，加深学生对这些概念的理解和运用．

DEMONSTRATION ON THE DIFFERENCE BETWEEN POLARIZED CHARGE AND FREE CHARGE

A group of vivid experiments has been demonstrated on the electrostatic induction phenomenon and polarization phenomenon by putting the conductor into electrostatic field and putting the insulator （dielectric） into static electric field, respectively. It has been shown that positive and negative charges polarized from dielectric cannot leave and move freely in the dielectric. Even if we make the dielectric with polarized charges touch the conductor, the polarized charges will not be neutralized by free charges of the conductor, which is to say, the polarized charges are bounded firmly in the dielectric. These results show the essential differences between polarized charge and free charge, which deepen the understanding and application of these concepts for students.