1)

 In a potentiometer experiment, the balancing length of a cell is 560 cm. When an external resistance of 10 Ω is connected in parallel to the cell, the balancing length changes by 60 cm. The internal resistance of a cell is 


A) 1.4Ω

B) 1.6Ω

C) 0.12Ω

D) 1.2Ω

Answer:

Option D

Explanation:

 Let us consider a cell of emf E and balancing length l1

 E=kl1

 potential difference is balanced by length  l2 , V= kl2

 r=(EVV)R=(EV1)R=(l1l21)R

 r=(560560601)10=(56501)10=65=1.2 Ω