Trystan Casey
Variable resistors are electrical components that can be adjusted to change their resistance value. They are used in electronic circuits to control voltage or current, allowing for the adjustment of factors such as volume, tone, bass, and brightness in devices such as radios, televisions, and speakers. Variable resistors are also used in motion control, transducers, computation, and home appliances. They can be made from materials like carbon, cermet, or wire and can be adjusted mechanically or digitally. The two main types of variable resistors are rheostats and potentiometers, which differ in the number of terminals they use and their primary function.
| Characteristics | Values |
|---|---|
| Definition | A variable resistor is a resistor of which the electric resistance value can be adjusted. |
| Working | It works by moving a wiper contact along a resistive track to change resistance, affecting current or voltage in a circuit. |
| Types | Rheostats, Potentiometers, Trimpots, Multi-Turn Potentiometers, Logarithmic Potentiometers, Conductive Plastic Potentiometers, MOSFET Variable Resistors, Cermet Variable Resistors, Memristors, Photoresistors, Thermistors, Humistors |
| Applications | Audio control, Television, Motion control, Transducers, Computation, Home electrical appliances, Radios, Speakers, Microphones, TVs, Oscillators, Smart home control devices, Dimmer switches for lights, Motor speed control, Automatic lighting control, Light-sensitive alarms, Amplifiers, Filters, Calibration circuits, Precision instruments, Laboratory equipment |
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What You'll Learn
Variable resistors are used to control voltage or current in a circuit
Variable resistors are a crucial component in electronic circuits, allowing for the adjustment of current or voltage. They are defined as resistors whose electrical resistance can be adjusted as needed. This is achieved by moving a wiper contact, also known as a slider, along a resistive track, which changes the length of the track and, subsequently, the resistance. The wiper is connected to a knob that can be adjusted manually to change the resistance between terminals.
Variable resistors are commonly used to control voltage or current in a circuit, and they come in two main types: rheostats and potentiometers. Rheostats are variable resistors with two terminals, while potentiometers have three. Rheostats are used to control current in a circuit, adjusting electrical resistance as required. They are connected in series with a load, such as a light bulb or motor, and by changing the position of the wiper along the resistance wire, the resistance in series with the load is altered, thus controlling the current. Potentiometers, on the other hand, are used to control voltage. They are often used in applications where voltage control is required, such as in audio equipment and televisions.
The various types of variable resistors include trimpots, multi-turn potentiometers, logarithmic potentiometers, conductive plastic potentiometers, MOSFET variable resistors, cermet variable resistors, and memristors. Trimpots, or trimmer potentiometers, are miniature variable resistors used for fine-tuning and calibration in electronic circuits. Multi-turn potentiometers offer increased precision by allowing multiple rotations for fine resistance adjustments. Logarithmic potentiometers provide a nonlinear resistance adjustment, making them suitable for audio equipment as they match human perception of volume changes. Conductive plastic potentiometers use conductive plastic tracks for resistance adjustment. MOSFET variable resistors provide voltage-controlled resistance, making them useful in signal processing applications. Cermet variable resistors, a type of potentiometer, are known for their stability and durability and are often used in precision applications. While memristors are not conventional variable resistors, they are an emerging class of two-terminal memory devices with variable resistance states.
Variable resistors have a wide range of applications in electronics and engineering. They are commonly used in audio control, television, motion control, transducers, computation, and home appliances. In audio control, they can adjust the volume, tone, bass, and treble of sound systems, radios, headphones, and speakers. In televisions, they can adjust the colour, brightness, contrast, and position of the picture. Variable resistors can also be used to convert physical quantities such as pressure, temperature, light, and sound into electrical signals. They are essential for tuning, calibrating, regulating, and modifying electronic circuits to achieve the desired output.
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They can be used as a rheostat or potentiometer
Variable resistors, such as rheostats and potentiometers, are used to control the amount of voltage or current flowing across an electrical circuit. They can be used as a rheostat or potentiometer, depending on the number of terminals connected.
A rheostat is a two-terminal variable resistor that adjusts current across a circuit. Rheostats are often used for controlling higher currents and are more mechanically robust when attached to a PCB due to having fewer terminals connected. They are typically constructed as wire-wound resistors, with resistive wire wound around an insulating ceramic core, and a wiper that slides over the windings. Rheostats were previously used as power control devices, such as light intensity (dimmer) controls, but have been largely replaced by more efficient switching electronics.
A potentiometer, on the other hand, is a three-terminal variable resistor that operates as a potential divider or voltage divider. It acts as two resistors in series, dividing the voltage and creating a new voltage value for the section of the circuit between the resistors. Potentiometers are commonly used in applications such as radio and television receivers, where they allow equipment to be switched on at minimum volume and then adjusted to a higher volume. They also find use in stereo audio amplifiers for volume control and in domestic light dimmers.
It is important to note that a potentiometer can be used as a rheostat by simply leaving one of its three terminals unconnected. This allows the potentiometer to function as a two-terminal device, controlling the current across a circuit.
In summary, rheostats and potentiometers are both types of variable resistors that can be used to control voltage or current in an electrical circuit. The main difference between them lies in the number of terminals they use and their primary function, with rheostats typically adjusting current and potentiometers acting as voltage dividers.
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$9.99
Variable resistors are found in many household devices
Variable resistors are commonly known as potentiometers or rheostats. Potentiometers are used to control voltage and are the most common type of variable resistor. They are often used in devices where voltage control is required, such as audio control and television. For example, a dimmer switch uses a variable resistor to control the brightness of a lamp by varying the current through the bulb. Linear variable resistors are preferred for television screens as they provide a more uniform change in picture quality. Rheostats, on the other hand, are used to control current and are less common today due to the advent of more efficient switching electronics.
Variable resistors are also found in motion control devices, such as motors, servos, fans, and pumps, where they can adjust the speed, direction, and torque. They are used in radio receivers and other tuning applications to adjust the circuit's resonant frequency for optimal reception and minimal interference. In addition, variable resistors are crucial for calibrating electronic instruments, allowing technicians to fine-tune devices for accurate measurements in scientific and industrial applications.
The versatility of variable resistors makes them applicable in various fields, including audio engineering, telecommunications, and automation. They are also cost-effective, user-friendly, and compact, making them easy to integrate into modern devices with limited space, such as smartphones and wearables. As a result, variable resistors are widely used in consumer electronics and industrial applications.
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They can be made from materials like carbon, cermet or wire
Variable resistors, also known as potentiometers, are used in many electronic applications. They are used for volume and gain controls, as well as in devices such as radios, speakers, microphones, and TVs.
Variable resistors can be made from materials like carbon, cermet, or wire. Carbon composition resistors are made from a mixture of carbon and a filler material, typically graphite, ceramic dust, and resin, or carbon dust or graphite paste with a binder like clay. After being pressed into sticks under high pressure and temperature, the mixture is baked to form a solid resistor body. Carbon composition resistors have been used for over a hundred years and are widely applied in circuits. They are advantageous due to their ability to withstand high energy pulses, but they have poor noise properties and a high temperature coefficient.
Cermet is a composite material consisting of ceramic and metal, making it suitable for high-temperature applications. Cermet resistors have good temperature stability, low noise levels, and good voltage ratings but low surge current properties.
Wirewound resistors are made by winding a thin metal alloy wire, such as Nichrome, onto an insulating ceramic former in the form of a spiral helix. They have very high wattage ratings and are used for heatsink mounting.
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Types of variable resistors include MOSFET, trimpots and multi-turn
A variable resistor is a resistor whose electric resistance value can be adjusted. Variable resistors can be controlled either mechanically (potentiometer, rheostat) or electronically (digital potentiometer).
Types of variable resistors include MOSFET, trimpots, and multi-turn. MOSFETs or metal-oxide-semiconductor field-effect transistors are intended for the linear region but are typically engineered for switching applications. While it is possible to use MOSFETs as variable resistors, precision is an issue as Rds would grow exponentially when Vgs approaches Vth.
Trimpots or trimmer potentiometers are small potentiometers used for adjustment, tuning, and calibration in circuits. They are designed for occasional adjustments and can achieve high resolution when using multi-turn setting screws. Single-turn trimmers are the most cost-effective variable resistors available, whereas multi-turn trimpots are used for higher adjustment resolutions.
Multi-turn variable resistors are often constructed using a worm-gear (rotary track) or lead screw (linear track) mechanism to achieve high resolution. They are more costly than single-turn preset resistors due to their complex construction and manufacturing.
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Frequently asked questions
A variable resistor is a resistor whose electrical resistance can be adjusted as needed. It is a three-terminal device that can adjust its resistance via the third terminal located between the other two terminals.
There are several types of variable resistors, including:
- Rheostats: These are variable resistors with two terminals that control the current in a circuit.
- Potentiometers: These are variable resistors with three terminals that control the voltage.
- Trimpots: Miniature variable resistors designed for fine-tuning and calibration in electronic circuits.
- Multi-Turn Potentiometers: Provide increased precision by allowing multiple rotations for fine resistance adjustments.
- Logarithmic Potentiometers: Provide a nonlinear resistance adjustment and are commonly used in audio equipment.
Variable resistors have a wide range of applications in electronics and engineering. They are commonly used in audio control, television, motion control, transducers, computation, and home electrical appliances. They can also be used to convert physical quantities such as pressure, temperature, light, and sound into electrical signals.
