# Nillsons Electrical Circuits Confusion

I'm reading this book Nilssons electrical circuits and I'm beginning to get frustrated/confused on some of the circuit diagrams. For instance this simple circuit with resistors in series. I understand that with Kirchoffs laws the sum of two currents at a node = 0 fair. But what I don't understand is why the drawings are drawn how they are (see below)

How is it possible with these resistors in series that current could travel seemingly randomly in opposite directions. R1 moves forward then R2 moves backwards then forward again. It's just really confusing me because I don't see how the current in a series of resistors can flip flop directions.

Nodes $$b$$ and $$g$$ violate the law unless one current of each pair is in the opposite direction. Nodes $$a$$, $$d$$, and $$f$$ do not violate the law; however the law does not say which direction the current flows. The currents at $$f$$ flow in the opposite direction to those in $$a$$ and $$d$$. However, we know that the direction for the current $$I_{S}$$ is correct because, by convention, current flows out of the positive terminal of the voltage source and there is only one voltage source in the circuit. Consequently, the actual direction of the currents at node f is opposite those shown. Then the direction of all currents will be the same.