【简答题】George worked in London. He wasn't married, and usually had his lunch, and sometimes his dinner, in small restaurants. One evening he decided to go to an expensive restaurant, and when he got in, he s...
【简答题】一种利用电容器测量油箱中油量的装置示意图如图12.4所示。附接电子线路能测出等效相对介电常量ε r,eff (即电容相当而充满板间的介电质的相对介电常量)。设电容器两板的高度都是a,试导出等效相对介电常量和油面高度的关系,以ε r 表示油的相对介电常量。就汽油(ε r =1.95)和甲醇(ε r =33)相比,哪种燃料更适宜用此种油量计?