A resistance of 20 is connected in the left gap of a metre bridge and an unknown resistance greater than 20 is connected in the right gap. When these resistances are interchanged, the balance point shift by 20 ~cm . The unknown resistance is

Step-by-step solution

Let the unknown resistance be R and the balance point be at l ~cm initially. using, R₂ R₁ = l 100-l Case 1: R₁=20 and R₂=R Using equation (1) and (2) we get, l 100-l = 80-l l+20 l=40 ~cm From equation (1), 20 R = 40 100-40 R=30