VITEEE 2015 Paper

Let us Consider a cell of emf E and balancing length l1
E = kl1
potential difference is balanced by length l2
V = kl2
Internal resistance of the cell
r = (

E−V

V

)R = (

E

V

−1) R = (

l1

l2

−1)R
= (

560

560−60

−1) 10 = (

56

50

−1)10
=

6

5

= 1.2 Ω