A cell can be balanced against `110 cm` and `100 cm` of potentiometer wire, respectively with and without being short circuited through a resistance of `10 Omega`. Its internal resistance is

Options

A. 2.0 ohm
B. zero
C. 1.0 ohm
D. 0.5 ohm

Answer

C

Explanation

`E prop I_(1) and E-(E)/(R+r),r prop l_(2)`
`rArr (r+R)/(R)=(l_(1))/(l_(2))`
`rArr r=((l_(1))/(l_(2))-1).R`
`=(110-100)/(100)xx10=1Omega`