bbgirl said:
Ah! Yes. And herein lies the reason for my confusion. I supposed I'm referring to electric current then but the diagrams are, of course, showing electron flow (which is opposite). Is that correct?
Scientists refer to both as "current". However, the flow of positive charges is sometime specified by the term "conventional current". I have heard the term "electron current" is occasionally used to specify the flow of negative charge.
You are talking about conventional current, while the diagram is showing "electron current". Some textbooks claim that "conventional current" should be the default meaning of current. From what you told us, some writers consider "electron current" to be the default meaning of "current".
Your textbook writers may treat the meaning of "current" as a context sensitive default. The assumption of many writers is that the reader knows the physical principles cold. Therefore, the reader can infer what specific convention to choose from the context of the first paragraph or from the diagram. Your diagram shows the flow of electrons. If the writer is self consistent, he should present the equations and wording consistent with "electron current".
Some writers are not consistent. I treat every use of the word current as a context sensitive default. That is, I always try to track what convention is being used from the local context while I read a chapter or article. If the writer makes a slips, or intentionally shifts gears, then I am ready. In the case of current, it isn't too hard to monitor context.
The defaults on the word "current" are relatively easy. One heads up. The convention becomes really important when the hand rules are presented. However, writers are usually try to be consistent when they use the word "current". I will shift to a related topic, while you aware of the problem.
Scientific jargon in general has ambiguities that are solved by convention. However, textbook writers sometimes don't assign a default meaning to a word. This creates confusion. For instance, there are several discussion threads going on right now concerning thermodynamics.
Thermodynamics has one of the worse ambiguities in jargon that I have ever seen. The word "heat" sometimes refers to "energy" and sometimes refers to "entropy". That is something that used to throw me every other time the word 'heat" was used. There is no formal default for the word "heat". Every time the word "heat" is used without a qualifier, I have to decide which meaning to use based on context alone. This is not really an ambiguity in the physics, but a problem in jargon.
