Q.

Space between the plates of a parallel plate capacitor of plate area 4 cm2 and separation of (d) 1.77 mm, is filled with uniform dielectric materials with dielectric constants (3 and 5) as shown in figure. Another capacitor of capacitance 7.5 pF is connected in parallel with it. The effective capacitance of this combination is ______ pF. (Given ε0=8.85×1012 F/m)        [2025]


Ans.

(15)

1C=1C1+1C2=d/2Ak1ε0+d/2Ak2ε0

    =(1k1+1k2)d2Aε0=(13+15)d2Aε0

1C=415dAε0

C=154×Aε0d

     =154×4×104×8.85×10121.77×103=7.5 pF

Finally equivalent capacitance (Ceq) = 7.5 + 7.5 = 15 pF