The equivalent resistance between the points A and B will be (each resistance is `15Omega`)

Options

A. `10Omega`
B. `40Omega`
C. `30Omega`
D. `8Omega`

Answer

D

Explanation

by eymmetry.
`R_("effective")` of `AE+EB and AB=30Omegaand15Omega` in parallel i.e `(1)/(30)+(1)/(15)=(1)/(10)`.
`R_(1)=10Omega`. Same for CED and CD . Therefore `15Omega,10Omega,15Omega` are in series in parallel with `AB_("effective")R_(1)`.
i.e., `(1)/(40)+(1)/(10)=(5)/(40)rArrR_("total")=8Omega`