Which type of voltage is represented by quick changes between on levels?

Digital voltage is characterized by having distinct, discrete levels that represent binary states, typically "on" and "off." This type of voltage is often involved in digital circuits and communication systems, where information is transmitted in the form of signals that switch between high and low states quickly. The concept of quick changes between these "on" levels aligns perfectly with how digital systems operate, as they effectively convey information through rapid transitions between two or more distinct voltage levels.

In contrast, analog voltage signifies continuous changes, where the signal can take on any value within a range rather than jumping between specific levels. Ground potential refers to a reference point in an electrical circuit against which voltages are measured and does not imply any rapid changes or discrete states. Electromotive force relates to the energy provided per charge by a source, often in a steady or gradually varying manner, rather than rapid changes. Therefore, digital voltage stands out for its unique ability to represent information through swift transitions, making it the correct answer.