Resistor Applications, Form Factors, and Types

Resisters perform an astonishing array of tasks within an electronic device

The most basic passive component, the resistor, may seem like a simple component with few applications. However, resistors have a range of applications, form factors, and types.

In this guide, we look at these resistors and provide you with an idea of when and where each is used.

Edison bulb
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Heaters

Joule heating is the heat created as current passes through a resistor. Often, this heat is an important factor in the selection of a resistor to ensure reliable operation. However, in some applications, the purpose of the resistor is to generate heat. The heat is generated by the interaction with the electrons flowing through a conductor, impacting its atoms and ions, essentially generating heat through friction.

Resistive heating elements are used in various products, including electric stoves and ovens, electric water heaters, coffee makers, and the defroster in a car. Resistive heaters are often coated with an electrical insulator to ensure that nothing shorts across the resistive element during normal operation. This is critical in electric water heaters that use submerged heating elements.

To maximize the effectiveness of a resistive heater, specialty materials such as nichrome, an alloy of nickel and chromium that is highly resistive and resistant to oxidation, may be used as the base resister material.

Fuses

Specially designed resistors are commonly used as single-use fuses. The conductive element in a fuse is designed to destroy itself once a certain current threshold is reached, essentially sacrificing itself to prevent damage to more expensive electronics.

Fuses are available with a range of properties to provide fast or slow response times, different current and voltage capacities, and temperature ranges. Fuses are also available in several form factors such as blade fuses (used in the automotive industry), glass-enclosed fuses, cylindrical fiberglass cartridge fuses, and screw-in fuses.

Resistive based fuses are affordable, and resettable fuse technologies reduce the burden on a user to find and replace a fuse. These fuses are often used in expensive equipment and in portable electronics that are not serviceable by the user and can absorb the higher cost of the resettable fuses.

Sensors

Resistors are often used as sensors for a range of applications, from gas sensors to lie detectors. A change in resistance may be due to liquid exposure, moisture, strain or flexing, and absorption of gas into the resistive material. By selecting the right material and enclosure, the performance of a resistive sensor can be tailored for a specific application and environment.

Resistive sensors are used as part of the suite of sensors on polygraph machines to monitor the perspiration of a subject. As the subject begins to perspire, a resistive sensor is affected by the change in moisture and provides a measurable change in resistance.

Resistive gas sensors function in the same way, with a greater presence of gas causing a change in the resistance of the sensor. Depending on the sensor design, self-calibration can be accomplished by applying a reference current to the sensor to remove all traces of the stimulating material.

For sensors that change little over the full range of the stimuli, a resistive bridge network is often used to provide stable reference signals for accurate measurements and amplification.

Light

Thomas Edison spent years searching for a material that would create a stable, electrically powered light. Along the way, he discovered dozens of designs and materials that would create some light and immediately burn out, much like a fuse sacrificing itself. Eventually, Edison found the right material and design to provide a continuous source of light. It became one of the largest and most important applications of resistors in history.

Today, alternatives exist to the original incandescent resistive light bulb design. Some, such as halogen lights, still rely on resistive-based designs. Incandescent lights are being replaced by CCLF and LED lights, which are more energy-efficient than resistive-based incandescent light bulbs.