An unknown resistance `R_(1)` is connected is series with a resistance of `10 Omega`. This combination is connected to one gap of a meter bridge, while other gap is connected to another resistance `R_(2)`. The balance point is at `50 cm` Now , when the `10 Omega` resistance is removed, the balanced point shifts to `40 cm` Then the value of `R_(1)` is.

Options

A. 20
B. 10
C. 60
D. 80

Explanation

`(R_1+10)R_2=50/50`……(i) [Case 1]
`R_1/R_2=40/60`…….(ii) [Case 2]
An solving (i) and (ii) we get `R_1=20 Omega and R_2=30 Omega`