Question

what is a rheostat? what does it do?

Answer 1

Answer: Rheostat is an electrical instrument used to control a current by varying the resistance.

Rheostat, adjustable resistor used in applications that require the adjustment of current or the varying of resistance in an electric circuit. The rheostat can adjust generator characteristics, dim lights, and start or control the speed of motors. Its resistance element can be a metal wire or ribbon, carbon, or a conducting liquid, depending on the application. For average currents, the metallic type is most common; for very small currents, the carbon type is used; and for large currents, the electrolytic type, in which electrodes are placed in a conducting fluid, is most suitable. A special type of rheostat is the potentiometer, an instrument that measures an unknown voltage or potential difference by balancing it, wholly or in part, by a known potential difference. A more-common potentiometer is simply a resistor with two fixed terminals and a third terminal connected to a variable contact arm; it is used for such purposes as a volume control in audio equipment.

Answer 2

To put it simply it is device which has a variable resistance that the varied according to the needs of the resistance. An example we use it in potentiometer experiment where we are needed to change the resistance during the experiment. The resistance can simply be changed by simply dragging the upper shaft like part of it over the coil.