Resistor Applications

Close-Up View Of Light Bulb
Sam Salek / EyeEm / Getty Images

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

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, but 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 a variety of products including electric stoves and ovens, electric water heaters, coffee makers, and even the defroster on your car. Resistive heaters are often coated with an electrical insulator to ensure that nothing will short across the resistive element in normal operation which is essential especially in electric hot water heaters that use a submerged heating element. To maximize the effectiveness of a resistive heater specialty materials are used such as nichrome, an alloy of nickel and chromium, that is highly resistive and resistant to oxidation.

Fuse

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

Resistive based fuses are very affordable but resettable fuse technologies reduce the burden on a user to find and replace a fuse and are often used in more expensive equipment and 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 wide range of applications from gas sensors to lie detectors. A change in resistance can be caused by a large number of factors including water and other liquids, 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 in real time as they undergo an examination. 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 very little over the full range of the stimuli, a resistive bridge network is often used to provide stable reference signals for more 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 itself out, much like a fuse sacrificing itself. Eventually, Edison found the right material and design that provided a continuous light which became one of the largest and most important applications of resistors for many decades.

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