Find the capacitance between A and B if two dielectric alabs (each of area `A`) of dielectric constants `K_(1)` and `K_(2)` and thicknesses `d_(1)` and `d_(2)` are inserted between the plates of a parallel plate capacitor of plate area `A`.
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Explanation

`C=(sigmaA)/(V)`
`V=E_(1) d_(1)+E_(2) d_(2)=(sigmad_(1))/(K_(1)epsi_(0))+(sigmad_(2))/(K_(2)epsi_(0))=(sigma)/(epsi_(0)) ((d_(1))/(k_(1))+(d_(2))/(k_(2)))`
`therefore C=(Aepsi_(0))/((d_(1)/K_(1)+d_(2)/K_(2)))`
`rArr 1/C=d_(1)/(AK_(1)epsi_(0))+(d_(2))/(AK_(2)epsi_(0))`

This formula suggests that the system between A and B can be considered as series combination of two capacitors.