I cannot seem to find a definitive answer as to how to treat voltage, amperes, resistance in formulas. Are they variables or abbreviations of units of measurement. It seems that they may be both depending upon the situation. For example voltage (V) in a formula but a volt (V) when proceeded by a number. Likewise; Amperes (A) or Amps (A). Current (I) seems to be variable but them measurement when converted to ohms (Ω). Resistance (R) also seems to be variable.
I would appreciate your input as I want to represent this information in the most understandable way for the student. I have attached a sample.
I'm posting again to acknowledge how very difficult it can be to determine whether a letter is a variable or an abbreviation, because print can use the same letter in both roles (i.e., A for "amperes" and also A for "unknown quantity of amperes").
It can require a lot of analysis on the transcriber's part to determine when a single letter is an abbreviation (as opposed to a variable) in a given mathematical expression.