Concept:For a parallel plate capacitor, capacitance is
C=dϵ0A When capacitors are connected in parallel, the equivalent capacitance is the sum of individual capacitances.
Explanation:Each capacitor has plate area
3A, so substitute this area in the formula.
For the first capacitor with separation
d:
C1=dϵ0(3A)=3dϵ0A For the second capacitor with separation
2d:
C2=2dϵ0(3A)=6dϵ0A For the third capacitor with separation
3d:
C3=3dϵ0(3A)=9dϵ0A In parallel combination, capacitances add directly:
Ceq=C1+C2+C3 Ceq=dϵ0A(31+61+91) Now,
31+61+91=186+3+2=1811.
Therefore,
Ceq=18d11ϵ0AAnswer:The equivalent capacitance is
18d11ϵ0A, which matches
Option C.