Resistor

Introduction To Resistor

The resistor is a passive electrical two-terminal electrical component that implements the electrical resistance as the circuit element. In electronic circuits, resistors are used to reduce the current flow, adjust the signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.

High-power resistors that can dissipate many watts of electrical power as heat, may be used as part of motor controls, in power distribution systems, or as test loads for generators. Fixed resistors have resistances that only change slightly with temperature, time, or operating voltage. Variable resistors can be used to adjust circuit elements (such as volume control or a lamp dimmer), or as sensing devices for heat, light, humidity, force, or chemical activity. The resistors are the most fundamental and commonly used of all the electronic components, to the point where they are almost taken for granted but they play a vital role within a circuit.

The main objective of a resistor within an electrical or electronic circuit is to “resist”, regulate or to set the flow of electrons (current) through them by using the type of conductive material from which they are composed. The resistors can also be connected together in various series and parallel combinations to form resistor networks which can act as voltage droppers, voltage dividers, or current limiters within a circuit.

The resistors are what are called “Passive Devices”, that is they contain no source of power or amplification but only attenuate or reduce the voltage or current signal passing through them. This attenuation results in electrical energy being lost in the form of heat as the resistor resists the flow of electrons through it. The resistors are what are called “Passive Devices”, that is they contain no source of power or amplification but only attenuate or reduce the voltage or current signal passing through them. This attenuation results in electrical energy being lost in the form of heat as the resistor resists the flow of electrons through it.

The resistance is measured in ohms, and it is symbolized by the Greek letter omega (Ω). Ohms are named after Georg Simon Ohm (1784-1854), a German physicist who studied the relationship between voltage, current, and resistance. He is credited for formulating Ohm’s Law.

I have experienced how the students are facing problems in their without understanding the basic concept and after engineering how they are struggling. So now I will explain a few basic points which will clear your most doubts.

Resistor:

The resistor is an electrical passive two-terminal resistive component which opposes the flow of current in a closed circuit.

Resistance:

The resistance is the capability of a resistor which defines the resistive power in Ohm.

There are two types of resistor available, such as

FixedType Resistor
Variable Resistor.

Fixed-Type Resistor:

The resistors whose resistance is constant means it made by the resistive material which can’t be changed. The fixed resistor is divided again into 4 types a

Carbon Composition Resistor.
Film or Cermet resistor.
Wire-Wound resistor.
Special resistor.

Carbon Composition Resistor:

This type of resistor is made of carbon dust or graphite paste, low wattage values. The Carbon Resistors are the most common type of Composition Resistors in the resistor family. Carbon resistors are a cheap general purpose resistor used in electrical and electronic circuits. Their resistive element is manufactured from a mixture of finely ground carbon dust or graphite (similar to pencil lead) and a non-conducting ceramic (clay) powder to bind it all together.

The Carbon Composite Resistor is low to the medium type power resistor which has a low inductance making them ideal for high-frequency applications but they can also suffer from noise and stability when hot. Carbon composite resistors are generally prefixed with a “CR” notation (eg, CR10kΩ ) and are available in E6 ( ± 20% tolerance (accuracy) ), E12 ( ± 10% tolerance) and E24 ( ± 5% tolerance) packages with power ratings from 0.250 or 1/4 of a Watt up to 5 Watts.

Carbon composite resistor types are very cheap to make and are therefore commonly used in electrical circuits. However, due to their manufacturing process, carbon type resistors have very large tolerances so for more precision and high-value resistances, film type resistors are used instead. When assembling electronic circuits, it’s important to use color coded resistors to ensure that the correct resistance values are being used.

Variable type Resistor:

The resistors whose resistance can be varied at any time inside the circuit is called as the variable type resister. The variable resistors are also categorized as two types are:

(1) Semi-Variable.

(2) Full Variable.

Working Principle of Resistor

A resistor works in a circuit by opposing the flow of electrical current, or by reducing the voltage of the signal passing through it. The amount of resistance a resistor provides is measured in ohms, and is determined by the material it is made from, its physical dimensions, and its temperature.

In a circuit, a resistor is typically connected in series with other components, such as a voltage source, a load, or another resistor. When current flows through the circuit, it encounters the resistance of the resistor, which causes a voltage drop across the resistor, according to Ohm’s Law. This voltage drop is proportional to the current passing through the resistor, and is given by V = IR, where V is the voltage drop, I is the current, and R is the resistance.

By changing the value of the resistance, a resistor can be used to control the amount of current flowing through the circuit, or to limit the voltage of the signal passing through it. For example, in a voltage divider circuit, two resistors can be connected in series to divide the voltage of a signal, with the ratio of their values determining the amount of voltage drop across each resistor.

Applications of Resistor

Resistors are used in many different applications in electronics, including:

Voltage Dividers: Resistors are commonly used in voltage divider circuits to divide a voltage into smaller parts.
Current Limiting: Resistors can be used to limit the amount of current that flows through a circuit, preventing damage to components.
Signal Conditioning: Resistors are often used in signal conditioning circuits to match the impedance of different components and ensure optimal signal transfer.
Timing: Resistors can be used in timing circuits to control the rate at which a capacitor charges or discharges.
Filtering: Resistors are used in filter circuits to attenuate certain frequencies and allow others to pass through.
Biasing: Resistors can be used in biasing circuits to establish a reference voltage or current level.
Temperature Sensing: Thermistors, which are a type of resistor, can be used to sense changes in temperature and provide a signal that can be used to control other components in a circuit.
Load Matching: Resistors can be used to match the impedance of a load to the output impedance of a driver circuit, ensuring optimal power transfer.
Sensing: Resistors can be used in sensing circuits to provide a voltage or current signal that varies in response to changes in a physical parameter, such as light or pressure. Ex: A light dependent resistor, also known as a photoresistor, is a type of resistor that changes its resistance based on the amount of light it is exposed to.
Attenuation: Resistors can be used to attenuate a signal, reducing its amplitude.

Advantages of Resistor

Some of the advantages of using resistors in electronic circuits include:

Precise Control: Resistors allow for precise control of the voltage, current, and impedance in a circuit, allowing for optimal performance and preventing damage to components.
Small Size: Resistors are available in a wide range of sizes, from tiny surface-mount components to larger through-hole components, making them suitable for use in a wide range of applications.
Low Cost: Resistors are relatively inexpensive, making them a cost-effective solution for many electronic circuits.
Low Power Consumption: Resistors consume very little power and generate very little heat, making them suitable for use in low-power and high-temperature environments.
Stable Performance: Resistors have a stable performance over time and under varying operating conditions, ensuring reliable and consistent operation in a circuit.
Wide Range of Values: Resistors are available in a wide range of resistance values, from very low values to very high values, making them suitable for use in a wide range of applications.

Disadvantages of Resistor

Some of the disadvantages of using resistors in electronic circuits include:

Heat Dissipation: When current flows through a resistor, it generates heat due to the resistance of the material. This can lead to temperature rise and potentially affect the performance of the circuit.
Non-ideal Characteristics: While resistors are designed to have a specific resistance value, in practice, they may have some deviation from the ideal value due to factors such as manufacturing tolerances, temperature changes, and aging.
Non-linear Response: Some resistors, such as thermistors, have a non-linear response to changes in temperature or other physical parameters, which can make them more difficult to use in certain applications.
Noise: Resistors can contribute to noise in a circuit, especially in high-frequency applications.
Limited Voltage Handling: Resistors are limited in the amount of voltage they can handle, and exceeding their voltage rating can cause damage or failure.
Limited Power Handling: Resistors are also limited in the amount of power they can dissipate, and exceeding their power rating can cause overheating or failure.

Future Development & Enhancement of Resistor

Resistors are a mature technology that has been widely used in electronic circuits for many decades. However, there are still opportunities for future development and enhancement, including:

Miniaturization: There is a growing demand for smaller and more compact electronic devices, which requires smaller components, including resistors. Advances in microfabrication and nanotechnology may enable the development of even smaller resistors with higher precision and performance.
Higher Precision: As electronic devices become more complex, there is a growing demand for higher precision resistors that can provide more accurate and consistent performance. Improvements in manufacturing techniques and materials may enable the development of resistors with even higher precision and stability.
Higher Power Handling: With the increasing demand for higher power electronics, there is a need for resistors that can handle higher power levels without overheating or failing. Advances in materials science and thermal management may enable the development of resistors that can handle higher power levels.
Integration with Other Components: As electronic devices become more complex, there is a growing need for components that can be integrated into a single package. Advances in packaging and integration technologies may enable the development of resistors that can be integrated with other components, such as capacitors and inductors, into a single package.
Smart Resistor: With the emergence of the Internet of Things (IoT), there is a growing need for sensors and smart components that can communicate with other devices and systems. Advances in microelectronics and wireless communication may enable the development of “smart” resistors that can provide feedback on their performance and adjust their resistance values based on external conditions.