DC Fundamentals Unit 11 – Potentiometers and Rheostats
A variable resistor using the wiper arm (center terminal) and only one end of the resistive
element is called a rheostat.
Rheostats are placed in series in a circuit to control circuit current.
Variable resistors are designed so that resistance varies when the shaft (or other adjusting device)
is rotated. The variation of resistance in relation to shaft rotation defines the taper of the variable
resistor.
With a linear taper, one-half rotation changes the resistance by one-half the maximum value.
Resistance change is linear (in a straight line) with respect to shaft rotation.