As a young engineering student many years ago, I was taught that an electrical energy source was comprised of an ideal generating element in series with an output impedance. The output impedance accounts for the fact that an internal voltage drop causes the output voltage to fall as load current is increased. It did not occur to me that this was, in reality, a simple mathematical model of a real generator. Only after being exposed to hydraulic circuits and symbols did I realize that they offer no clues as to how the system inefficiencies operate to affect overall system performance. The analytical aspects of the componentry were, at best, only implicit in the symbology. This is clearly inadequate for mathematical modelling of the system.