The word potentiometer originally meant a device for measuring electric potential differences. Later, it also was applied to a tapped resistance used as a voltage divider. Although the measuring instrument is no longer used in undergraduate labs, it is the only truly perfect voltmeter, drawing no current and thus appearing to have an infinite impedance. There is some good physics and history connected to it, and so it is an appropriate subject for a historical tutorial.
“The Potentiometer”, The Physics Teacher, 43, 232-235 (2005)
The Physics Teacher