Types of Resistors

Types of Resistors
Types of Resistors

Resistors are essential electrical circuit components that resist current flow. These passive two-terminal devices limit circuit current and component voltage. Electronics, telecommunications, power supplies, and industrial equipment employ resistors. Engineers and technicians must understand resistor types to choose the right one for circuit design and troubleshooting.

You presumably know that electrical circuits need resistors. Without these tiny components regulating current flow, most electronics would short circuit or overheat in seconds. But did you realize there are many resistors for different applications? This tutorial covers fixed resistors for LED circuits and thermistors for temperature-sensitive alarm systems. We’ll cover the most popular resistors, from carbon comp to light-activated photoresistors. By the end, you can choose the right resistor for any project. Let’s explore resistors’ beautiful universe.

Introduction

Resistors are essential electrical circuit components that inhibit current flow. They manage voltage, current, divide voltages, and more. Variable resistors can be modified, while fixed resistors have stable resistance.

Permanent Resistors

Fixed resistors have a fixed resistance. The most common resistors are carbon composition, metal film, and wirewound. Carbon-composition resistors are cheap yet inaccurate. Metal film resistors are more reliable. High-power wirewound resistors.

Variable Resistors

Potentiometers and rheostats have adjustable resistance. As voltage dividers, potentiometers have a fixed maximum resistance. Though comparable, rheostats handle more current. Trimmers are small variable resistors for precision resistance adjustments.

Specialized Resistors

Thermistors have temperature-dependent resistance, varistors prevent voltage spikes, and photoresistors change resistance with light. Thermistors measure temperature, varistors protect circuits, and photoresistors sense light.

Many types of resistors meet different demands. They regulate current flow in a circuit by providing a fixed or adjustable resistance. Next time you turn on a light or change the radio volume, thank resistors!

Carbon Metal Film, Wirewound Fixed Resistors

Three types of fixed resistors include carbon composition, metal film, and wirewound. Look at each type.

Carbon composition resistors are solid cylinders of carbon and filler materials. These cheap, high-power devices are inaccurate and noisy. Use only if precision isn’t important.

Thin metal films on insulating ceramic substrates form metal film resistors. They are precise, stable, and quiet. However, they cost more and can’t handle as much power as carbon comp resistors. Precision and power handling make metal films an all-purpose choice.

Carbon, Metal Film, Wirewound Fixed Resistors
Carbon, Metal Film, Wirewound Fixed Resistors

Wirewound resistors have ceramic or plastic tubes wrapped in wire. They handle high power and precision best. They’re pricey, bulky, and inductive. When precision, power, and frequency response matter, use wirewounds.

If cost matters, choose carbon comp resistors. Choose metal film for precision and stability. If power and precision are equal, wirewounds are best. Understanding the benefits and downsides of each type lets you choose the correct fixed resistor.

Potentiometers, Rheostats, Trimmers

The name implies variable resistors offer adjustable resistance. They help you manually manage circuit voltage or current. Trimmers, potentiometers, and rheostats are the main types.

Potentiometers, Rheostats, Trimmers
Potentiometers, Rheostats, Trimmers

Potentiometers

Three-terminal potentiometers are variable resistors. Volume knobs, dimmer switches, and thermostats use them to control voltage. A wiper glides along a resistive strip in pots to tap off resistance. Two outer terminals link to the resistive strip ends, while the middle terminal connects to the wiper. Pots are ideal for frequent manual adjustment.

Rheostats

Rheostats control current via two-terminal variable resistors. They work like pots but have two connections. High-power applications like motor speed control use rheostats. They make it easy to manually increase or reduce resistance to vary circuit current.

Rheostat
Rheostat

Trimmers

Trimmers, often called preset potentiometers, are variable resistors with a screw or wheel to set the resistance. Adjusted resistance stays fixed unless manually reset. During manufacture and assembly, trimmers calibrate or “trim” circuits to precise voltage or current values. They provide minor resistance modifications for circuit tuning.

Variable resistors allow circuit control that fixed resistors cannot. Variable resistors can be used to change settings, regulate high power loads, or fine-tune voltage levels.

Photoresistors, Varistors, and Thermistors

Unique features make specialized resistors valuable for specific applications. Thermistors, varistors, and photoresistors.

Thermistors

Resistance changes with temperature in thermistors. Positive temperature coefficient (PTC) thermistors increase resistance as temperature rises, while negative temperature coefficient (NTC) ones decrease. Overheated PTC thermistors are utilized as resettable fuses because their resistance spikes. NTC thermistors are common in temperature control circuits. Resistance changes predictably with temperature.

Varistors

Varistors, also called voltage-dependent resistors (VDRs), are insulators at low voltages but conduct at a breakover value. Often used to prevent voltage spikes, they clamp voltage to a fixed level. When the spike subsides, the varistor returns to high resistance. Varistors absorb a lot of energy for their size but degrade with voltage spikes.

Photoresistors

Photoresistors (LDRs) change resistance with light. Material resistance is high in the dark but low in light. Light meters, automatic lighting controls, and light sensor circuits use photoresistors.

Thermos, varistors, and photoresistors are specialized resistors with temperature, voltage, and light exposure-dependent resistances. They are helpful for temperature monitoring, surge prevention, and light sensing due to their unique features. The variety of resistors makes it easy to choose one for your next project.

Electrical Circuits with Different Resistors

Electrical circuits and devices use resistors extensively. The circuit’s needs determine the resistor type.

Electrical Circuits with Different Resistors
Electrical Circuits with Different Resistors

Permanent Resistors

Circuits often limit current flow or voltage with fixed resistors like carbon composition or metal film resistors. They limit LED current in circuits. Circuits with fixed resistors include amplifiers, timers, and power supply.

Variable Resistors

Potentiometers and rheostats are handy for manual resistance adjustment. Audio volume controls and display brightness controls employ potentiometers. Lighting dimmers use rheostats for high power management.

Specialized Resistors

Resistors with specific characteristics serve specific functions. Temperature sensors and compensators employ thermistors. Varistors safeguard delicate components from voltage spikes and surges. Light detecting circuits like cameras and outdoor lighting employ photoresistors.

Resistors are simple but essential in many electronic devices and circuits. For maximum performance, the right resistor—fixed, variable, or specialized—reaches the desired current, voltage, or resistance. You’ll find the right resistor for your next project with so many alternatives.

Conclusion

You now understand the most common resistors. You can choose a typical fixed resistor for a simple circuit or a tailored resistor for a complex project using this information. Little electronic parts have essential functions, as you’ve seen. You’ll understand pots, thermistors, and varistors better next time you’re constructing a circuit, visiting an electronics store, or talking to other makers. The resistive world is now obvious.

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