A potentiometer wire of length 1m and resistance `10 Omega` is connected in series with a cell of emf 2V with internal resistance `1 Omega` and a resistance box including a resistance R. If potential difference between the ends of the wire is 1 mV, the value of R is

Options

A. `20000 Omega`
B. `19989 Omega`
C. `10000 Omega`
D. `9989 Omega`

Answer

B

Explanation

`V =IR =(2/(1 + 10 + R)) xx 10`

`rArr 10^(-3) = 20/(11 +R)`
`rARr R = 19989 Omega`