In a potentiometer circuit when two cells of e.m.f. 1.5 volt and 1.2 volt are connected to assist each other, balancing length is 270 cm. What will be the balancing length in cm when these two cells are connected in opposition?

Step-by-step solution

Let the potential gradient of the potentiometer wire be k . When the cells assist each other, the equivalent EMF is E₁ + E₂ . E₁ + E₂ = k l₁ 1.5 + 1.2 = k 270 2.7 = 270 k When the cells are connected in opposition, the equivalent EMF is E₁ - E₂ . E₁ - E₂ = k l₂ 1.5 - 1.2 = k l₂ 0.3 = k l₂ Dividing the two equations, we get: 2.7 0.3 = 270 l₂ 9 = 270 l₂ l₂ = 30 cm Answer: 30