9.单选题-|||-如图,一平行板电容器两极板间距为l,面积为S,-|||-在两极板之间放置一厚度为h的金属板。设两-|||-极板带电量分别为 pm 0 ,不计边缘效应,两极板间-|||-的电势差() ()-|||-h |-|||-(A) dfrac (Ql)(2{varepsilon )_(0)s}-|||-(B) dfrac (Qh)({S)_(0)S}-|||-(C) dfrac (Q(1-h))({varepsilon )_(0)S}-|||-(D) dfrac (Q(1-h))(2{varepsilon )_(0)S}