Component Spotlight: The Resistor

What is a Resistor?

A resistor is an electrical component that, as the name implies, provides electrical resistance to a circuit. A resistor is opposite to a conductor, where a conductor allows the flow of electrons, a resistor opposes it. The amount of electric resistance is measured in a value called Ohms.

What purpose does a resistor serve in circuits?

A resistor is an electrical component used for many different purposes in electronic applications. Mostly they are used to reduce current but can be used for other means such as absorbing power in motor braking, to act as an electrical load, or even as a thermal sensor to name a few others.

More advanced resistors such as potentiometers and rheostats can even act in switching and changing current variably. This kind of resistor is used in devices such as tuning knobs, volume controls, power regulators and other current over range applications.

What can cause a resistor to fail?

The main killer of resistors is heat. When a resistor becomes hot its ability to dissipate heat is reduces and will suffer damage from the thermal runoff. The most common reason for this is access current supplied to the circuit that is higher than the power rating of the resistor being used. This power rating for resistors is measured in watts. This is usually caused by other components in the circuit failing and not the resistor itself, as resistors have a relatively low failure rate on their own. Components such as capacitors and transistors failing can cause resistors to fail on the same circuit. In addition, contaminants such as dust and oil can also cause resistors to overheat due to these acting as a thermal insulator.

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