Figure shows a potentiometer arrangement with `R_(AB)=10 Omega` and rheostat of variable resistance d. For `x=0` null deflection point is found at `20 cm` from `A`. For unknown value of `x` null deflection point was at `30 cm` from `A`, then the value of x is

Options

A. `10Omega`
B. `5Omega`
C. `2Omega`
D. `1Omega`

Answer

B

Explanation

`E_0=V_(AC)=(i)_(AC)(R)_(AC)`
`=(E/10)(10/1xx0.2)`
`=E/5`
In second case,
`E_0=((E)/(10+x)) ((10)/1xx0.3)`……….ii
Solving eqn i and ii we get
`x=5Omega`