Electrical Current
In an electrical circuit, electrons move from one side, or terminal, of a power source to an opposite terminal. The power source provides a certain amount of potential energy, or voltage, to the circuit, and the flow of electrons through the circuit is the electrical current. Current measures the rate at which electric charge passes through a single point in the circuit, and is measured in amps. Resistance is also present in all electrical circuit. Resistance, measured in ohms, is just what its name suggests. It is resistance to the flow of electricity in a circuit.
Function
A rheostat varies resistance in an electrical circuit. Ohm's law dictates that this will also affect the current in an electrical circuit. As resistance in a circuit is increased, current decreases. Conversely, current in a circuit increases as resistance decreases. An operator can manually adjust the resistance of a rheostat, thus regulating the current flowing through the circuit.
Construction and Operation
A rheostat consists of a coil of electrically conductive material often wrapped around a ceramic core. Though the coil does conduct electricity, it also introduces resistance into the circuit. A linear rheostat has its coil wrapped around the length of its core, while a rotary rheostat has its coil wrapped into a circular shape. A user operates a rheostat by moving a slider or knob that is connected to an electrically conductive wiper that makes contact with the coil. As the wiper moves along the coil, it increases or decreases the length of coil that electricity flows through. When electricity flows through a longer section of coil, it encounters more resistance. The entire rheostat is enclosed in a case to keep dirt out and to protect users from electrical shock.
Applications
Rheostats are typically used in light dimmer switches and to control the peed of motors. But a rheostat can be effective in any electrical device that can vary its output according to the voltage it receives. For instance, light connected to a rheostat will shine more brightly when more voltage flows to it through the circuit.