[sacrosancty]

That 2nd distinction seems weirdly unreal. Is there an example of a real generic voltage source that only uses electrical energy and not those other types, or are you just referring to an idealization that you might use in a circuit diagram?

[projektfu]

Many voltage sources are themselves circuits and the EMF element would be hidden therein.

[sacrosancty]

Hmm. So is it that an EMF can't be carried along conductors like voltage can and is only the original source of the electrical energy with no circuitry?