板间每一半介电体可认为是一个电容器, C1=E1S/(d/2)=2E1S/d C2=E1S/(d/2)=2E2S/d C1与C2是串联关系,总电容C, 1/C=1/C1 +1/C2 C=C1C2/(C1+C2)=2E1E2S/(E1+E2)d
