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The effective resistance between points ...

The effective resistance between points P and Q of the
electrical circuit shown in the figure is
(a) `(2Rr)/(R+r)`
(b)`(8R(R+r))/(3R +r)`
(c) `2r + 4R`
(d) `(5R)/2 + 2r` .
.

A

`(2Rr)/(R+r)`

B

`(8R(R+r))/(3R+r)`

C

`(2r+4R)`

D

`(5R)/2+2r`

Text Solution

Verified by Experts

The correct Answer is:
A
a. The circuit is symmetrical about the axis PQ. Therefore, the
equivalent circuit is
`1/R_(PQ) = 1/(4R) + 1/(4R) + 1/(2r) = 1/(2R) + 1/(2r)(R+r)/(2Rr)`
or `R_(PQ) = (2Rr)/(R+r)`
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