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What Is a Power Resistor?

Carbon resistors offer “fixed” amount resistance to a circuit.
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  • Written By: Alexis W.
  • Edited By: Heather Bailey
  • Last Modified Date: 21 October 2014
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Found in virtually any electrical device that contains a controlled circuit board, a power resistor is used to control the current that flows through a circuit. A power resistor works to dissipate voltage for instruments in some circuits that require a lower amount of energy than others. Resistors basically protect delicate elements within a circuit by lowering the amount of voltage or current delivered to them. A power resistor can also assist the process of reducing electrical noise generated by the introduction of energy to a circuit and can create tolerance and stability throughout the circuit by helping to distribute the power signal to where it needs to be.

Resistors are manufactured from numerous materials, and come in many sizes, depending on the resistance requirements of the application they are used in. Some resistors can even be a simple wire, when the wire is manufactured from naturally resistant material like the alloy nickel-chrome. They can also look very similar to filament fuses, though they don’t typically contain any glass parts.

Usually visible as small multi-colored cylinders with a wire protruding from each end, a power resistor can be formatted into any type of circuit board. This means a power resistor can be used in either a printed or integrated circuit board. The size of a resistor is directly determined by the resistance requirements of the circuit, as the resistor must be large enough to keep from overheating as it performs its duties.

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If the incorrect resistor is placed within a circuit and it is unable to successfully provide the resistance needed, it may overheat over time and become damaged, not performing its function properly. If this occurs, each unit in the continuing sequence of the circuit may become overloaded and overheat as well, damaging the entire circuit and rendering the electronic device dysfunctional or even useless. If the resistor is too big for the amount of resistance it must provide, it may underpower the circuit, also resulting in the device not working due to lack of power.

Resistors may even come in an adjustable form, which reduces the chance of overheating or underpowering the circuit in which they are placed. These types of resistors usually have multiple connection terminals to provide different resistance levels according to the needs of the circuit. The amount of resistance provided can be altered by simply changing the location of the connection points on the multiple-point terminal for the resistor.

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