On Wikipedia, voltage is defined to be the electric potential difference. However, I am still not certain as to whether voltage is the electric potential ($PE/q$) or electric potential change ($\Delta PE/q$).
My confusion partially comes from talking about circuits and defining the amount of volts a point in a circuit has.
So, is voltage electric potential or its change? If voltage is the change of electric potential, then how can one point in a circuit be measured in volts?
Best Answer
This is potentially confusing, and an excellent example of sloppy terminology perpetuated by careless textbook authors. One should never substitute a quantity's unit for the name of that quantity. We never ask people about their "yearage" when we mean age or "footage" when we mean height. We frequently, however, use "mileage" as a substitute for fuel efficiency, which is also incorrect. Add to this that too many authors use the same symbol for both electric potential and electric potential difference.
The physical quantity here is electric potential, which is a comparison of electric potential energy and electric charge and is represented by the symbol $V$. This quantity constitutes a scalar field around charged particles. Each point in space has assigned to it a value for electric potential. The difference in electric potential between any two points is called an electric potential difference and is represented by the symbol $\Delta V$. Too many authors use $V$ to represent both quantities, but this is erroneous because they are different quantities and are not interchangeable despite having the same unit, volt. To make matters even more confusing, the volt is denoted by the symbol $\mathrm{V}$, which is too similar to the symbol used for electric potential. Electric potential difference is directly measurable with a multimeter but electric potential is not.
The bottom line is that one should never substitute a quantity's unit for that quantity. Call the quantity what it is, electric potential or electric potential difference, and use distinct and unambiguous symbols.