People who insist that all charge is carried by electrons have never worked on a ion implant machine (as used in the semiconductor industry).

But, of course, that's only when the carriers are not in a conductor.

 

People who insist that all charge is carried by electrons have never worked on a ion implant machine (as used in the semiconductor industry).

TV engineers are well aware of positive ion current - it plannishes the cathode coating in the CRT.

There are apparently also negative ions, before CRTs had aluminised phosphor, they had to angle the electron gun so the negative ions collided with the inside of the tube neck. The ions were too heavy to deflect with a magnetic field, so that's what was used to steer the electron beam back on course through the deflection system and on to the phosphor.

 

The first main practical effect of initially having reversed the positive and negative designations to the correct value from what they are now, would be when dealing with vacuum tubes.
In that case (with electrons being designated as having positive charge) then the first tube (valve) circuits would have used a negative supply (assuming cathode to common) and all the carriers (positive electrons) would have flowed from the common to the negative supply terminal.
Thus we would have needed to think in terms of current flowing from the bottom to the top of the schematic (assuming the common would still be placed at the bottom).

This would have likely continued with solid-state circuits, with negative power supplies and the carriers going from common to the supply (except notably for ECL circuits which generally used opposite polarity supplies).
Personally I think that would be harder to visualize then our present system of positive carriers from positive (supply) to negative, but perhaps that's just because I've thought top to bottom (sort of a water analogy) all my life.

Or would we have invented imaginary (now negative) carriers so we could still have the carriers going from top to bottom?

My guess is that we would still have charge flow from positive to negative and that positive would still be at the top of the schematic by convention. The symbols and naming conventions would merely have evolved to be compatible with that.

 

The reasoning here is actually backwards. No current flows through R6 because there is no path through the ground node back to the other end of V3. Since no current can flow there can be no voltage across R6.

Ok. But is it not true that due to the fact that full voltage drop happens across R3 leaving no potential at negative terminal of V3?

Just as all of the nodes connected to a common (ground) symbol are actually the same node, you can assign a name to a node (called a "net name") and all nodes with that same name are connected together. Rethink your answer with this in mind.

Yes. I assumed that 4th circuit and 6th have no relationship but missed the fact that the node "mike" connects them together.
So, 4 ma flows through the resistor R4

Your reasoning is fine, but you aren't expressing if correctly. The reference, by definition, is 0V, so it makes no sense to say that the reference is 5V (and if you DO say that, then the voltage at node5 would have to be 0V, do you see why). The V5 supply between COM and node5 is such that
(Vcom - Vnode5) = 5V
Vcom = 0V
Vnode5 = -5V

Sure. Thanks.

At this point you start going off the rails:

But you accurately described that the current in R6 would be zero previously, so where are you getting -1/1000 (which should be -1V/1000Ω -- units matter).

My mistake. Actually, I was actually referring to the figure in the previous post of Mike and trying to answer.

Again, this didn't give you problems earlier. Where is the 1 volt coming from.

Again, same mistake. I was referring to the previous post of Mike.