Questions like this one are potentially on-topic on Electrical Engineering. However, that question is a little too basic for most of our users, and we don't get a lot of homework questions as it seems you do per this meta post on homework and "no question is too basic, but we won't do your homework". We do occasionally get questions which seem to be from people learning about electricity in physics classes, though.

Is that an example of a good, on-topic question on Physics? Where do you draw the line between questions like this (which is just a voltage divider attached to some voltage sources) and off-topic problems better suited for another site like Electrical Engineering?

Do you want us to refer questions like this to your site, or do you want to refer questions like this to us?

Also, a heads up: that question just got tweeted, so make sure it's nice and pretty according to your standards.

  • $\begingroup$ arrgh, stupid automated Twitter script... anyway, thanks for asking this. I have my own thoughts which I'll post later, but in the meantime I'll be interested to see what the community thinks about this. $\endgroup$
    – David Z
    Commented Oct 21, 2011 at 14:21
  • $\begingroup$ @DavidZaslavsky - I have the same love-hate relationship with the Twitter script. It seems to pick the worst questions. Then, if they get any traction, they get re-tweeted by the main StackExchange twitter account, which drives even more traffic. This one, fortunately, didn't get re-tweeted by that account. Why does USB have 4 lines instead of 3? is the 2nd-highest voted question on Electrical Engineering; it doesn't deserve that. $\endgroup$ Commented Oct 21, 2011 at 14:29

2 Answers 2


Seeing as how nobody else has piped in here: a question like this is on topic at this site, but not a good question, at least not as of revision 2 (before I edited it just now). It was one of those questions which presents a homework problem and then basically says "I'm confused" without any attempt to explain what exactly is causing the confusion. My edit (based on information the OP provided in a comment) improves it enough to save it from being close-worthy IMO, but it's still not great.

It's been my understanding that EE.SE is mostly for questions about building and analyzing systems out of complex electronic components, not just simple circuits. Given that simple circuits are discussed in most introductory electromagnetism (physics) classes, I would say it's generally fine for you to migrate questions about them over here. If they wind up having quality problems such that we need to edit them or close them, that's okay.

To clarify, by "simple circuits" I mean anything involving only

  • batteries or other DC sources (though in physics "battery" is used to refer to a generic DC source)
  • generators or other AC sources
  • resistors (including devices which act as resistors, such as light bulbs)
  • capacitors
  • inductors
  • ammeters and voltmeters

In particular, diodes and transistors are not treated in most physics classes, at least not as circuit elements. Questions about how those components work at the subatomic level are on topic here at PSE, but questions about the behavior of circuits which include transistors or diodes are likely not.

Any question which refers to a specific make and model of electronic component is also almost certainly off topic here.

If you're not sure about something, you can always leave a message in our chat room.

  • $\begingroup$ I wouldn't go so far as to migrate all "simple" circuit questions here, but this does seem like a good breakdown of the differences between the sites. Also, the use of "batteries", "generators", and "light bulbs" in a schematic does seem to be an indicator that whoever's asking the question is probably in a Physics course. :) $\endgroup$ Commented Oct 22, 2011 at 22:13
  • $\begingroup$ OK, fair enough - of course any question you think is on topic at EE, go ahead and keep it. I was really just trying to explain what sorts of circuit questions are on topic here at Physics. It sounds like there might be a small overlap in what we consider on topic in this area. $\endgroup$
    – David Z
    Commented Oct 22, 2011 at 22:16

Yes, that's a good question because there's a lot of physics in a good answer to it:

  • what is potential difference?
  • how do we measure it?
  • How does a charge lose energy travelling through a resistance?
  • can a charge be taken through a battery?
  • why do we sum voltages to find the total voltage?

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