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