Three resistances P, Q, R each of `2Omega` and an unknown resistance S form the four arms of a Wheatstone's bridge circuit. When a resistance of `6Omega` is connected in parallel to S, the bridge gets balanced. What is the value of S?

Options

A. `2 Omega`
B. `3 Omega`
C. `6 Omega`
D. `1 Omega`

Answer

B

Explanation

The bridge formed with given resistance is a balanced Wheatstone's bridge the situation can be depicted as shown in figure.
As resistance S and `6Omega` are in parallel their effective resistance is
`(6S)/(6+S) Omega`
or `2/2=(2(6+S))/(6S)`
or `3S=6+S`
or `S=3Omega`