Circuit Stories

 This is  my answer  to SE EE question  What actually flows, current electricity or charge ? My answer To intuitively understand circuits, it is enough to realize that something like a pump (source) produces something like pressure (voltage) that causes something like fluid (electric current) to flow from where it is a lot (the positive source terminal) to where it is a little (the negative terminal) encountering obstacles (resistance) on its way. Then we need to realize what the connection between these pressure-like, flow-like and impediment-like quantities is (Ohm's law) and to see where currents flow (topology). Finally, it remains to be seen (in a most general way) what the basic circuit idea is.

I dedicate this story to my students from group 48a (see also a related RG discussion  and Codidact paper ) Need to visualize currents I have long understood that one of the most important techniques to understand circuits is to see where currents flow inside them (in circuit theory, this is considered unimportant and, at best, currents are represented by small arrows with arbitrary direction). First ideas The problem is that currents, like other electrical quantities, are invisible... and to show them, we have to visualize their paths, directions and magnitudes. That is why, in the late 80's , for the purposes of true understanding, I began representing current paths on circuit diagrams through closed directed lines. An example is the circuit diagram of an op-amp inverting amplifier from my Student Manual for the Analog Circuitry (1989): Another electrical "law" Even then, I realized how important is to draw power supplies because currents start from the positive termina...