Q.

A capacitor is made of a flat plate of area A and a second plate having a stair-like structure as shown in the figure. If the area of each stair is A3 and the height is d, the capacitance of the arrangement is:      [2024]

1 11ϵ0A18d  
2 13ϵ0A17d  
3 11ϵ0A20d   
4 18ϵ0A11d  

Ans.

(1)

All capacitors are in parallel combination.

Also, effective area is common area only

Ceq=C1+C2+C3

=ϵ0A3×d+ϵ0A3×2d+ϵ0A3×3d

=6ϵ0A+3ϵ0A+2ϵ0A18d=11ϵ0A18d