Question

It is required to decide the ratio (e₁ / e₂) by sum and difference method also. Four cells with different values of emf E are available. One must use a cell of emf E equal to 

(a) 1.40 V  (b) 2.0 V  (c) 4.5 V  (d) 1.08 V 

Answer 1

Correct option  (c) 4.5 V

Explanation:

Ratio of emfs :  e₁/e₂  = l₁/l₂   

Ratio of emfs by sum and difference method : e_{1 +} e₂/e₁ - e₂ =  l₁/l₂ = e₁/e₂  = l₁ + l₂ /l₁ - l₂  

The emf of the cell used in the primary circuit should be greater than (e₁ + e₂) E > (1.4 + 1.08)

E > 2.48 volt