reostaty

Reostaty, also known as rheostats, are adjustable resistors used to control current in an electrical circuit by varying resistance. They are typically two-terminal devices, though some designs provide a third terminal for use as a potentiometer in divider mode. The essential component is a resistive element—often carbon or a wire-wound conductor—with a sliding or rotating contact (a wiper) that moves along the element to change the effective resistance.

Construction and operation: A rheostat consists of a resistive track and a contact mechanism mounted in a housing. In rotary rheostats, a knob rotates a contact over a circular track; in linear types, a slider moves along a straight element. The user set point determines the resistance, which in turn controls current according to Ohm’s law. Because the device dissipates electrical power as heat, its power rating (in watts) and cooling requirements limit the practical range of operation.

Types and ratings: Rheostats are available in high-power and low-power forms. High-power models use wire-wound elements and substantial heat sinking for applications such as motor speed control or heater regulation. Carbon-based and other resistive elements are common in lower-power variants. The selection depends on required current, voltage, and permissible temperature rise.

Applications and history: Historically important in laboratory experiments, industrial controls, and early audio equipment, rheostats provided a simple means to adjust current. In modern electronics, solid-state controllers and dimmers have largely supplanted rheostats for many uses, but they remain in use where straightforward, rugged, high-current resistance adjustment is needed, such as in some motor controllers and heating systems.