A
rheostat is basically a variable resistor generally having two terminals.
Though Rheostats can be used as series resistors or potentiometers but there
are some differences between a Rheostat and a Potentiometer. Rheostat is
essentially a single variable resistor and typically causes current to vary
with the variation in resistance and controls the amount of current flowing
in a circuit. Also, Rheostats are much bigger and designed in a fashion for
handling much higher voltage and current.
Rheostats are are designed in a way for handling very high voltage and
current. Rheostats are manufactured as a resistive wire which is wrapped to
form a toroid coil. A wiper is made to move over the top surface of the
toroid, sliding from one turn of the wire to the other. Many a times a
Rheostat is constructed from a resistance wire. The resistance wire is wound
on a heat resisting cylinder. The slider is manufactured using a number of
metal fingers which grips very lightly onto a small portion of the turns
found in a resistance wire. By sliding a knob the 'fingers can easily be
made to travel along the coil of resistance wire. In this way there is a
change in the 'tapping' point
Types of Rheostat
Rotary
Rheostat
A Rotary Rheostat essentially consist of a resistance element, a rotatable
slider and a bearing. The resistance element ia typically a wire-wound ring.
The current supply to the rotatable slider can be provided through a sliding
contact or a spiral spring. The sliding contact construction is relatively
simple and provides the advantage of relatively easy assembly of the
individual parts.
Sliding
Rheostat
Sliding Rheostats are popular in physics lab experiments that needs
changing of the resistance or electric current. As compared to a rotary
Rheostat, Sliding Rheostats provide better monitoring of the adjustments
made on a rectilinear scale.
Rheostat with Double Runner
Rheostat with Double runner is employed for altering the current intensity
or also can be used as potentiometers for altering the difference of
potential. A Rheostat with Double runner featured here is manufactured by
using slate prisms with a wire wound on them. It is supported by a metallic
frame and two different cursors. The design of the terminal boards
facilitate connecting of the two resistances in parallel or series. Thus
permitting a larger use of the Rheostat. An unique data plate applied to the
cursor of the Rheostat warns about the total resistance and current that can
be sustained by the rheostat for the short interval without any risk.
