# How to determine the directions of voltages across resistors in circuit diagrams?

In the following diagram, the directions of both currents and voltages for voltage sources are shown. My task is to write KCL and KVL for all 3 loops, and my question concerns KVL.

I believe I am approaching KVL problems wrong, this is precisely how I think:

If we look at R2 in loop Is1, for example, we can se that both U02 and U01 are directed to it. I assumed R2's direction would be opposite to the run of Is1, since it would take the direction of the voltage with higher magnitude, U01. But in the correct KVL equation it has the same direction as the run.

Moreover I don't understand where to start the loop: should it be where the arrow is (in loop Is1 it would be R1) o do I start with the node?

• @Nare, use KVL equations, Eq(0+100-r1*(is1)-20-r2*(is1-is2),0) and Eq(0-r2*(is2-is1)+20-r3*(is2)-r4*(is2),0), in Python/Sympy. Solves for the two loop currents, trivially. The rest is a distraction. Commented Oct 4, 2023 at 3:36