A resistance of `2Omega` is connected across one gap of a meter bridge (the length of the wire is `100 cm`) and an unknown resistance, greater than `2Omega`is conneted across the other gap. When these resistances are interchanged, the balance point shifts by `20 cm`. Neglecting any corrections,the unknown resistance is

Options

A. `3Omega`
B. `4Omega`
C. `5Omega`
D. `6Omega`

Answer

A

Explanation

`Rgt2Omegabecause100-xgtx`
applying `(P)/(Q)=(R)/(S)`
we have `(2)/(R)=(x)/(10-x)`
(i). `(R)/(2)=(x+20)/(80-x)`
solving equation (i) and (ii) get `R=3Omega`