Two cells when connected in series are balanced on 8 m on a potentiometer. If the cells are connected with polarities of one of the cell is reversed, they balance on 2 m. The ratio of the cmf’s of the two

Let the EMFs of the two cells be E₁ and E₂.
In series: E₁ + E₂ ∝ 8 m
With one reversed: E₁ – E₂ ∝ 2 m
Solving, (E₁ + E₂) / (E₁ – E₂) = 8/2 = 4.
Solving gives E₁ / E₂ = 3/5.
Correct answer: (a) 3 : 5.
Class 12th Science Physics NCERT MCQ Questions
NCERT Books MCQ Questions Session 2024-2025.