1. The problem statement, all variables and given/known data 2. Relevant equations For R, current I=E/R and for X, I=E/X... both are seperate cases. 3. The attempt at a solution Why does the balancing change? The potential difference across each resistor is E Itself right? I tried by assuming an arbitary internal resistance r. but in the book, it given as: E2/E1 = iX/iR but how is I same in this case when resistance is varied? They have given that I is the current in potentiometer wire.... but how does the that current cause potential difference across R? It should the current E/R or E/X that passes through R and X.