I'm reading an introductory E&M textbook (with an electrochemical emphasis, so charge carriers are ions rather than electrons), and the wording my book uses to describe current is giving me a great deal of confusion that I was hoping someone could help me resolve. My understanding is as follows:
charge: [itex] q, [/itex] in units of Coulombs (C).
current: the rate of flow of charge; [itex] i = \frac{dq}{dt}[/itex], in units of C/s.
current density (or current flux): the rate of flow of charge per unit area; [itex] J = lim_{A \rightarrow 0} \frac{i}{A}, [/itex] where the limit converges about a point, in units of C/s/area.
My confusion is when the book uses phrases such as: "Current flows from the positive terminal to the negative terminal..." and "The current flow through the membrane..." I don't understand how a time rate of change (i.e., current) can "flow" anywhere at all, when it is the charge carriers that are physically moving. In my eyes, it is sort of like saying that automobile velocity flows through the tunnel --- but the velocity isn't flowing through the tunnel, the automobiles are. It seems like the correct phrasing should be "charge flow" in both cases. Am I mistaken?
Or, another possibility I'm worried about is that I'm misinterpreting "current flow" in the sense that it really means "current flux." When people say "current flow," are they actually referring to current flux? Are current flow and current flux the same thing?
I guess my question is: if someone were to say, "current flows from the positive terminal to the negative terminal," should this (1) be viewed as sloppy wording and interpreted actually to mean that positive charge flows from the positive terminal to the negative terminal, or (2) be interpreted to mean that a current flux exists that is directed from the positive terminal to the negative terminal? Because viewing it literally as current flow seems meaningless to me.
Thanks
charge: [itex] q, [/itex] in units of Coulombs (C).
current: the rate of flow of charge; [itex] i = \frac{dq}{dt}[/itex], in units of C/s.
current density (or current flux): the rate of flow of charge per unit area; [itex] J = lim_{A \rightarrow 0} \frac{i}{A}, [/itex] where the limit converges about a point, in units of C/s/area.
My confusion is when the book uses phrases such as: "Current flows from the positive terminal to the negative terminal..." and "The current flow through the membrane..." I don't understand how a time rate of change (i.e., current) can "flow" anywhere at all, when it is the charge carriers that are physically moving. In my eyes, it is sort of like saying that automobile velocity flows through the tunnel --- but the velocity isn't flowing through the tunnel, the automobiles are. It seems like the correct phrasing should be "charge flow" in both cases. Am I mistaken?
Or, another possibility I'm worried about is that I'm misinterpreting "current flow" in the sense that it really means "current flux." When people say "current flow," are they actually referring to current flux? Are current flow and current flux the same thing?
I guess my question is: if someone were to say, "current flows from the positive terminal to the negative terminal," should this (1) be viewed as sloppy wording and interpreted actually to mean that positive charge flows from the positive terminal to the negative terminal, or (2) be interpreted to mean that a current flux exists that is directed from the positive terminal to the negative terminal? Because viewing it literally as current flow seems meaningless to me.
Thanks