Herr Barth, I have to agree with Mr. Siegel in this case. He is showing us with a red colored shorting bar between the switches and bulbs how both bulbs will 'light' when either of the two switches are in the closed position, when without the short, only one bulb should 'light' depending on with switch is closed.
Mr. Lane, I took the time to read portions of Khan Academy tutorial. I found it interesting, but for me a bit confusing. As best as I can tell, the author is giving answers to students thinking of entering the field of electrical technology. What he is describing as 'Conventional flow' is what, at the time, we called 'hole flow'. It was an instructors attempt to describe what was going on at the boundary of a p-doped and n-doped semiconductor. Heavy stuff for a beginner.
