The most prominent use of rheostats as already discussed is to control the current. All other applications are mostly derived from this very current controlling property of the rheostat. To limit the current so as to prevent high current faults, these rheostats are used. According to the current requirement the size of the rheostat to be used is chosen. For example, for high current circuits, large rheostats are used. They are also used in dimmer circuits,
Speed control circuits for motors, heaters and ovens. Since they dissipate heat, they have low efficiency and hence are now being replaced by pulse width controlled switching devices. Preset rheostats or the trimmers are used during calibration or circuit tuning. In case two terminal trimmers are not available, a three terminal trimmer potentiometer is wired as trimmer rheostat.

Use of rheostat

Some of the learners also asked:
What is the SI unit of resistivity?