To write the correct equations, describing processes in an electric circuit or its elements, we must set conventional positive direction of EMF, currents in all the branches, and the voltage between the junctions, and at the terminals of the circuit elements.
For the currents in the circuit's branches, which contain EMFs, the direction must be coinciding with the direction of the EMF; in all other branches, the direction may be arbitrarily.
For voltage drop across circuit’s elements or branch, the direction must be coinciding with the direction of the current in the branch or circuit element.
