In the following figures, area of each plate is `A` and `d` is separation between adjacent plates. Find the capacitance of system between points `A` and `B`.

Explanation

To solve, first give numbers to plates as `1,2,3`,…. Next , make new diagram by placing `A` and `B` and connect plates to `A` and `B`.
(a) with plate `2`, two capacitors are formed, `(2,1),(2,3),` with plate `3, (3,4)`. Plate `2` is connected to `A` and plate `3` to `B`. Plates `1` and `4` are connected by a wire.
`C_(eq)=(c)/(2)+C=(3C)/(2)=(3Ain_(0))/(2d)` `["since" C =(Ain_(0))/(d)]`
(b) `C_(eq)=(2C.C)/(2C+C)=(2C)/(3)=(2)/(3)(Ain_(0))/(d)`
(c) `C_(eq)=2C=(2Ain_(0))/(d)`
(d) `C_(eq)=4c=(4Ain_(0))/(2d)`
`C_(eq)=(2C)/(3)+C=(5C)/(3)=(5Ain_(0))/(d)` .
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