What is a Rheostat?
A rheostat is the device that is most commonly used in dimmer switches for lighting fixtures. A rheostat works using an adjustable resistor between the electricity supply and the device that can use adjustable current like a light fixture or volume control.
How Does a Rheostat Work?
A rheostat has a coiled wire that provides resistance. One end of this wire is connected to a live feed wire, while the other end isn’t connected to anything. There is also another wire that is called a wiper, which is responsible for making sure the current reaches its load.
The rheostat functions using the principles of Ohm’s law. This law dictates that the current is inversely proportional to resistance for a given voltage. What this means is as the resistance increases, the current decreases. So once current enters the rheostat, it flows through the coil and exits. This process allows objects such as dimmer switches to produce a decreased output.
Construction of a Rheostat
There are two different types of rheostats: straight and rotary. A straight rheostat has a coil that is pulled straight. The rotary type is coiled tightly to save space. These coils are sealed inside a case which provides protection from outside elements, such as moisture and dirt. Rheostats are typically crafted from carbon disks or metal ribbons. However, any material that has the ability to stay durable during intense changes can be used to create rheostats.
Rheostats are designed to handle smaller currents. For example, you wouldn’t want to use this device with a heater blower, which requires a stronger current to reach the load. Make sure to select this device for smaller projects, like dimmer switches.
A triac is commonly used instead of the rheostat. The rheostat can fail because contact surfaces become dirty and coil wires become corroded. However, devices like the triac have better reliability and don’t consume as much energy.