Bright Bulb Resistor
What is Rheostat
A rheostat is electrical equipment that has an adjustable resistance. This equipment is defined as a type of potentiometer that has two terminals instead of three. There are two main types of this equipment namely rotary and slider. It has a symbol, which is a resistor with an arrow diagonally across it. These equipments are mainly used in many different applications that will include light dimmers and motor controllers in large industrial machines. Most of these machines are the wire wound type that has a long length of conductive wire, which is coiled into a tight spiral.
The linear types have straight coils while the rotary type has the coil curved into a torus in order to save space. The coil and contacts are sealed inside the case to protect them from dirt, which may cause an open circuit, and from the moisture, which is capable of causing short circuits. These equipments can be made from other materials such as metal ribbons, carbon disks as well as certain fluids. Any material that has a significant resistance change over a short length can probably be used to make these equipments.
The basic principle used by these equipments is Ohns law that states that current is inversely proportional to resistance for a given voltage. This will mean that the current will decrease if the resistance increases or it will increase as the resistance decreases. Current enters these equipments through one of its terminals, flows through the wire coil and contact and exits through the other terminal. These equipments do not have polarity and they operate the same even when the terminals are reversed. Three terminal potentiometers can be used by connecting the unused third terminal to the contact terminal to represent an example of these equipments.
These equipments can be applied in several platforms an this will include as light dimmers in order to limit the current passing through the light bulbs and hence change their brightness. The greater resistance of these equipments, the lower the brightness will be from the light bulbs. However, some lights cannot use dimmers and these will include fluorescents as well as gas discharge lamps as they have large resistance loads known as ballasts. These ballasts maintain a constant current through them and this will mean that these equipments will not have an effect on their brightness and in worse scenarios can even damage them.
These equipments can also be used by motor controllers in order to control the speed of a motor by limiting the flow of current through them. The equipments can also be used in several small appliances that will include fans, mixers, blenders as well as power tools. Testing of instruments can also be done using these equipments in order to provide an accurate resistance value. These equipments can also be used to control electric ovens as well as cook tops although thermostats are the most proffered because they have additional parts that automatically adjust the current floe in order to maintain a constant temperature.
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This article touched the basics of the topic. I have 2 more resources related to the above. They are
rheostat
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basic electronics
. They are worth a read.
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