Variable resistor and its application area

A variable resistor or, as it is also called, the rheostat is intended to adjust the resistance of an electrical circuit in order to obtain the required value. Depending on its design features, it can change the resistance both smoothly and in stepwise order.

Usually a variable resistor is used in various kinds of equipment and devices. It can be seen as a volume knob, as a lighting control, etc. At the same time, its application area is so large that at the present time there is practically no electrical device that, one way or another, would not be equipped with a variable resistor.

There are four main types of rheostats, which differ from each other constructively, but perform the same functions.

The first type represents wire resistors. They are very common and can clearly show the principle of operation of all variable resistors. The essence of their work lies in the fact that the wire wound on the frame is energized, and with the help of the third contact it is removed from various places of the frame. Naturally, in each specific place the resistance will be different.

The second type is a variable-slider resistor. It is made of wire, which has a large resistance, it is regulated in the same way as in wire resistors. However, there are differences. In a wire resistor, the voltage is removed from the contacts, which provides a step change in the resistance, and in the slider this change occurs smoothly, since the slider freely slides along the wire.

The third type is a variable resistor that uses an electrolyte. To do this, the resistor contacts are immersed in it, and the adjustment is made by changing their distance.

One of the most obvious and simple types of variable resistors is a lamp. It consists of parallel connected lamps, and the resistance changes in it by turning them off or on. Such a variable resistor is very inaccurate and unreliable, since its values directly depend on the degree of heating of the lamp, and therefore can vary with time.

It is worth noting that thanks to the rheostat it is possible to change not only the resistance, but also the current and voltage. For this, the variable resistor is connected to the electrical circuit in parallel or in series, depending on the need to change a particular parameter.

Thus, the variable resistors used to control the amperage can be called rheostats, and the resistors for voltage regulation are called potentiometers. It is these that are used as regulators for the volume of sound, output voltage, power, etc. On their basis, a large number of different types of linear and angular displacement sensors have been constructed.

Due to their qualities and properties, variable resistors are considered one of the foundations of modern electronics and electrical engineering.