1. The problem statement, all variables and given/known data The following circuit is given. I intend to calculate the current in every resistor (every quantity except i1, i2, i3, is known). My textbook states that ℰ3-ℰ1 = (R1+R2+R3+R4+2r)*i, but I think it should be -ℰ3+ℰ1 on the left-hand side, since the current enters the negative and leaves the positive terminal of ℰ1 and does the opposite with ℰ3. 2. Relevant equations Ohm's generalized law for a closed circuit (the algebric sum of the emf's equals R*i, where R is the total resistance) 3. The attempt at a solution I've simply computed the same equation of the book, but I don't understand why my signs are wrong.