In a potentiometer experiment of a cell of emf 1.25 V gives balancing length of 30 cm. If the cell is replaced by another cell, balancing length is found to be 40 cm. What is the emf of second cell ?

Options

A. `~= 1.57 V`
B. `~= 1.67`
C. `~=1.47`
D. `~=1.37 V`

Answer

B

Explanation

`E_(1) alpha l_(1)`
`E_(1)alpha l_(2)`
`(E_(1))/(E_(1)) = (l_(1))/(l_(2)) rArr (1.25)/(E_(2)) = (30)/(40) rArr E_(2) = (5)/(3) = 1.67 V`