A slab of material of dielectric constant K has the same area as that of the plates of a parallel plate capacitor but has the thickness d/2, where d is the separation between the plates.Find out the expression for its capacitance when the slab is inserted between plates of capacitor.

Capacitance of parallel plate air capacitor is given by,C0=0AdCapacitance of capacitor when its plates are partly filled with dielectric of thickness t and same area as the plates,C=0Ad-t(1-1K)Here,t=d2So, C=0Ad-d2(1-1K)=0Ad2+d2K=0AdK+d2K=0A×2Kd (K+1)=2KK+10AdOr C=2KK+1C0Thus, capacitance becomes 2KK+1times of initial capacitance.

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