Resistor, construction, types, SI unit, uses

What is resistor?

A resistor is an electrical component used to limit or control the flow of electrical current in a circuit. It is designed for a specific electrical resistance, measured in ohms (symbol: Ω). Resistors are passive components, meaning that they do not produce or amplify electrical signals, but rather control the current. Resistors can be made from a variety of materials depending on the intended application and desired properties.

Materials used in the construction of resistors are:

Some common materials used in the construction of resistors are:

Resistors can be made of different materials.Usually modern resistors are made of carbon film, metal or metal oxide.In these resistors, a thin film of conductive (albeit resistive) material is wrapped and covered with an insulating material.

These are just a few examples of the different materials used in the construction of resistors. Each material has its own characteristics and is selected based on factors such as desired resistance value, power, temperature coefficient, stability and cost.

What is a resistor in the SI system?

Ohm is the SI unit for a resistor.

Types of resistor:

Linear Resistor:

A linear resistor is a basic passive electronic component that has a linear relationship between the applied voltage and the current flowing through it. This means that the resistance value remains constant regardless of the voltage or current value. Linear resistors have a fixed resistance value and follow Ohm's law, where the current through the resistor is directly proportional to the voltage across it.

Nonlinear Resistor:

A nonlinear resistor, also known as a variable resistor or a nonlinear device, is a resistive component whose resistance value changes nonlinearly with applied voltage or current. In other words, the resistance of a nonlinear resistor changes nonlinearly as the voltage or current changes. Non-linear resistors have a non-constant resistance characteristic and the relationship between voltage and current is non-linear.

Nonlinear resistors can have different characteristics such as resistance that changes with temperature (thermistors), resistance that changes with intensity of light (photoresistors or LDRs), resistance that changes with the strength of an external magnetic field (magnetoresistors), or resistance that varies depending on the intensity of the external magnetic field (magnetoresistance). changes based on other factors. These resistors provide a means of introducing non-linear behavior into electronic circuits for specific purposes such as sensing, control, or compensation.

Linear resistor and its types:

In electronics, a linear resistor refers to a base resistor that has a constant resistance value regardless of the applied voltage or current. Linear resistors are the most common type of resistor and are widely used in electronic circuits.

Here are some types of linear resistors:

Carbon compound resistor:

This type of resistor is made by mixing carbon particles with an alloy material and molding them into a cylindrical shape. Carbon composite resistors have a linear resistance characteristic and are commonly used in low power applications.

Film Resistor:

Film resistors consist of a resistive material deposited on an insulating substrate. Typical examples are metal film and metal oxide film resistors. These resistors offer excellent linearity and are available in a wide range of resistance values.

Wirewound Resistor:

Wirewound resistors are made by wrapping resistive wire, usually made of an alloy such as nichrome, around a ceramic or fiberglass core. They have a linear resistance characteristic and are mostly used in high power applications where accuracy and stability are required.

Thin Film Resistor:

Thin film resistors are made by applying a thin layer of resistive material to a substrate. They offer high accuracy, stability and linearity. Thin film resistors are often used in applications where accurate resistance values are important.

Metal Oxide Film Resistor:

Metal oxide film resistors are similar to carbon film resistors but use metal oxide instead of carbon as the resistance material. They provide good linearity, stability and stability. Metal oxide film resistors are commonly used in a wide variety of electronic devices.

Fusible Resistor:

Fusible resistors are designed to be used as a protective element in the event of excessive current. They have a built-in fuse that opens (breaks the circuit) when the current exceeds a certain threshold. Fused resistors are often used in applications where safety is paramount.

It is important to note that all these types of resistors have a linear resistance characteristic,

Types of non-linear resistor:

Nonlinear resistors, also known as variable resistors or nonlinear devices, are resistive components whose resistance value changes nonlinearly with applied voltage or current. They show a non-linear relationship between voltage and current. Here are some types of nonlinear resistors:

Thermistor:

A thermistor is a type of resistor whose resistance changes significantly with temperature. There are two common types of thermistors: positive temperature coefficient (PTC) thermistors and negative temperature coefficient (NTC) thermistors. PTC thermistors show an increase in resistance with temperature, while NTC thermistors show a decrease in resistance with temperature. Thermistors are widely used for temperature measurement, temperature compensation and temperature control.

Varistor:

A varistor is a voltage-dependent resistor that has a non-linear resistance characteristic with respect to voltage. Its resistance decreases significantly when the applied voltage exceeds a certain threshold value. Varistors are used for surge protection and transient voltage suppression in electrical and electronic circuits.

Photoresistor (Light Dependent Resistor or LDR):

A photoresistor is a photosensitive resistor whose resistance changes according to the intensity of the light falling on it. The resistance of a photoresistor decreases with increasing light intensity and vice versa. Photoresistors are commonly used in lighting control and light sensing applications.

Magnetoresistor:

A magnetoresistor is a resistor whose resistance changes in response to an external magnetic field. The resistance of a magnetoresistor increases or decreases depending on the strength and orientation of the magnetic field. These resistors are used in various applications such as magnetic field sensors, compasses and positioning systems.

Positive Temperature Coefficient (PTC) Resistor:

PTC resistors have a positive temperature coefficient of resistance, which means that their resistance increases with temperature. These resistors are often used in self-resetting circuit protection applications such as overcurrent protection or thermal overload protection.

Negative Differential Resistance (NDR) Resistor:

NDRs are special types of resistors that have a region of negative differential resistance on an I–V curve. This means that the current decreases as the voltage increases over a certain voltage range. NDR resistors are used in certain applications such as oscillators, amplifiers and switching circuits.

These are a few examples of nonlinear resistors, each with their own unique characteristics and applications. They provide a means of introducing nonlinear behavior into electronic circuits for specific purposes such as sensing, control, and protection.

Application/Uses:

Resistors are basic electronic components used in a wide variety of applications. They are designed to introduce resistance into an electrical circuit that controls the flow of current and voltage. Here are some common uses for resistors:

Voltage Division:

Resistors are used in voltage dividers to get a portion of the input voltage. This is useful in various applications such as analog signal conversion, level shift and offset.

Current Limiting:

Resistors are used to limit the current in a circuit. They are often used in series with an LED to prevent excessive current from damaging the LED, or in series with a transistor to set the transistor's operating point.

Load Resistor:

Resistors are used as load resistance in circuits to simulate a specific load or to dissipate power. For example, they can be used as dummy loads in audio amplifiers or as pull-up/pull-up resistors in digital circuits.

Temperature Sensing:

Some types of resistors, such as thermistors, change their resistance with temperature. They are used in temperature sensors and thermostats to monitor and control temperature in various applications.

Filtering:

Resistors are used in conjunction with capacitors and inductors to form RC and RL filter circuits. These circuits are used to filter unwanted frequencies or attenuate signals in audio systems, power supplies and communication systems.

Timing and Generation:

Resistors are used in timing circuits such as RC timing circuits to control the charging and discharging rate of capacitors. They are also used in conjunction with capacitors and inductors to set the frequency and damping factor in oscillator and resonant circuits.

Voltage and current measurement:

Precision resistors with known values are used as reference resistors or shunt resistors to accurately measure voltage and current. They are commonly used in instrumentation, power supplies and feedback control systems.

Pull-up/Pull-up Resistors:

Resistors are used as pull-up or pull-up resistors in digital circuits to provide a certain logic level when the input signal is not being actively driven. It is commonly used in microcontroller interfaces and digital communication protocols.

Noise Reduction:

Resistors can be used in circuits to reduce noise by introducing resistance and dissipating unwanted electrical energy. This can be seen in applications such as amplifier circuits, audio systems and signal processing circuits.

These are just a few examples of the many applications of resistors. They are versatile components and play a vital role in the design and construction of electronic circuits.

What are the applications of resistors in our daily life?

Most of the circuit-based devices in our homes use resistors, such as remote controls, cell phone chargers, TVs, hair dryers, etc.
Resistive filaments have been used in electrical equipment such as heating rods, kettle, iron, light bulb, etc.