一、原理教学上使用的粉笔写字板,写和擦都很费劲,粉沫横飞,对老师和同学身体健康危害极大,加上对比不明显,这就要求我们对写字板进行彻底改革,制做既能克服上述缺点,又使用方便,还经济耐用的写字板。下面所述便是这样一种写字板。有些液晶,在适当的外加电场中,某些光学性质发生变化,例如向列相液晶,光的反射率或透射率发 First, the principle of teaching the use of chalkboard, write and rub are very laborious, Fenmo fly, great harm to the health of teachers and students, coupled with the obvious contrast, which requires us to carry out a radical reform of the tablet, To do both to overcome the above shortcomings, but also easy to use, but also economical and durable tablet. Described below is such a tablet. Some liquid crystals, in the appropriate applied electric field, some of the optical properties change, such as nematic liquid crystal, light reflectivity or transmittance