What is a resistor?

Building the circuit needs an understanding of numerous components, including resistors, transistors, diodes, inductors, capacitors, battery sources, and connecting wires. A resistor is one of the circuit's primary components.

What is Resistor?

A resistor is an electrical component that resists the flow of electrical current, used to regulate voltage levels and control the amount of current flowing in a circuit. They are typically made of materials such as carbon or metal and are available in various sizes and resistance values. They are one of the most basic and widely used electronic components in circuit design.

What is the SI Unit of Resistor?

The SI unit of resistance is the ohm (Ω). It is the resistance between two points in a conductor when a constant potential difference of 1 volt is applied to these points, and the resulting current is 1 ampere. The ohm is named after the German physicist Georg Simon Ohm, who studied the relationship between current, voltage, and resistance.

Types of Resistors

There are many different shapes and sizes of resistors. Surface mount and through-hole are two of the most common types. A resistor can be static, a standard resistor, a special resistor, or a set of variable resistors.

There are two main kinds of resistors, which are:

• Linear resistor
• Non-linear resistor

Linear Resistor

A linear resistor is a type of resistor whose resistance value remains constant over a wide range of applied voltage or current. This means that the resistance is directly proportional to the applied voltage or current, and the resistance-voltage or resistance-current relationship is a straight line. Linear resistors are commonly used in a wide range of applications, including amplification, filtering, and voltage regulation. They are also used in circuit protection, such as fuses and PTC (positive temperature coefficient) thermistors. Linear resistors can be made from various materials, such as carbon film, metal film, wire wound, and metal glaze. Linear resistors are found in most electronic devices including computers, smartphones, and televisions.

Non-Linear Resistor

A non-linear resistor is a type of resistor whose resistance value does not remain constant over a range of applied voltage or current. This means that the resistance is not directly proportional to the applied voltage or current, and the resistance-voltage or resistance-current relationship is not a straight line. Non-linear resistors are not commonly used in the same applications as linear resistors, as their non-linear characteristics can introduce distortion or other unwanted effects in a circuit. Examples of non-linear resistors include thermistors and varistors.

Thermistor

A thermistor is a non-linear resistor whose resistance changes with temperature. They are commonly used in temperature sensing applications and temperature compensation in electronic circuits.

Varistors

A varistor is a non-linear resistor whose resistance changes with voltage. They are commonly used to protect electronic circuits from voltage spikes, such as those caused by lightning strikes. When a voltage spike occurs, the varistor's resistance drops, allowing the spike to be safely dissipated to ground.

Diodes, transistors and other semiconductor devices can also exhibit a non-linear resistance behavior depending on the bias conditions and are also called as non-linear resistors.

There are also several types of resistors, each with their own unique characteristics and uses. Some of the most common types include:

Carbon Film Resistor

Carbon film resistors are one of the most common types of resistors and are widely used in electronic circuits. They are made by depositing a thin layer of carbon onto a ceramic rod or substrate. The resistance value of the resistor is determined by the thickness and resistance of the carbon film.

These resistors are inexpensive, have good stability, and a wide range of resistance values. They are also commonly used in low-power applications, as they have a low power rating. The tolerance of carbon film resistors is typically in the range of 5% to 10%. They also have a relatively low-temperature coefficient, meaning that their resistance value does not change significantly with temperature.

Metal Film Resistor

Metal film resistors are a type of resistor made by depositing a thin layer of metal, such as nickel-chromium, onto a ceramic rod or substrate. They have higher stability and a better temperature coefficient compared to carbon film resistors and a lower tolerance of typically 1% to 2%. They are commonly used in high-precision applications such as measuring instruments, amplifiers, and control circuits, as well as in applications where stability and temperature coefficients are important, like temperature control systems and power supplies. However, they are relatively more expensive than carbon film resistors.

Wirewound Resistor

Wirewound resistors are made by winding a wire, usually made of nickel-chromium alloy, around a ceramic or metal rod. They have a very high power rating, making them suitable for high power applications, and good stability. The resistance value is determined by the wire material, number of turns, and diameter of the wire. Wirewound resistors also have a low tolerance, typically around 1%, making them precise. However, they are relatively more expensive than other types of resistors. Wirewound resistors are commonly used in power supplies, audio equipment, and high-power industrial applications where a high power rating and stability are required.

Metal Oxide Resistor

Metal oxide resistors are made by coating a ceramic rod with a metal oxide material, such as zinc oxide. They have a high power rating, good stability, and a low-temperature coefficient, meaning that their resistance value does not change significantly with temperature. The resistance value is determined by the composition of the metal oxide material and the thickness of the coating. Metal oxide resistors also have a low tolerance, typically around 1%. They are relatively expensive compared to other types of resistors. Metal oxide resistors are commonly used in high-power applications where stability and temperature coefficients are important, such as in power supplies and temperature control systems.

Composition Resistor

Composition resistors are a type of resistor made from a mixture of carbon and other materials, such as metal powders or ceramics. They are formed into a solid cylindrical shape and are coated with a protective material. Composition resistors have a medium power rating, good stability, and a low-temperature coefficient. The resistance value is determined by the composition of the mixture and the size of the resistor. Composition resistors have a relatively low tolerance, typically around 5% to 10%. They are less expensive than metal film or metal oxide resistors but more expensive than carbon film resistors. Composition resistors are commonly used in a wide range of applications, including power supplies, amplifiers, and digital circuits.

Film Resistor

Film resistors are a type of resistor made by depositing a thin layer of material, such as carbon or metal, onto a ceramic or metal rod. The resistance value is determined by the composition and thickness of the film. Film resistors have a range of power ratings and stability, depending on the type of film used. Carbon film resistors are typically less precise but less expensive, while metal film resistors are more precise but more expensive. Film resistors also have varying temperature coefficients, with metal film resistors having a lower temperature coefficient compared to carbon film resistors. Film resistors are widely used in a variety of electronic applications, including power supplies, amplifiers, and digital circuits.

Foil Resistor

Foil resistors are a type of precision resistor made by depositing a thin layer of metal, such as nickel-chromium, onto a flat ceramic substrate. The resistance value is determined by the composition and thickness of the metal film. Foil resistors have a high stability and a low temperature coefficient, meaning that their resistance value does not change significantly with temperature. They also have a low tolerance, typically around 0.1%, making them very precise. Foil resistors are relatively expensive compared to other types of resistors, and are commonly used in high-precision applications such as in measuring instruments, amplifiers, and control circuits.

Variable Resistor

Variable resistors, also known as potentiometers, are resistors with a resistance value that can be adjusted manually. They are commonly used as a way to adjust the resistance in a circuit to control the current flow, voltage drop, or to adjust the gain in amplifiers. Variable resistors can be of different types, including wirewound, carbon, or metal film. They are constructed with a rotating shaft or slider that changes the resistance value, and the resistance can range from a few ohms to several kilo-ohms. Some variable resistors are designed for precision applications, while others are designed for more rugged and high-power applications. They are commonly used in a wide range of applications, including volume controls in audio equipment, adjusting brightness in light dimmers, and as sensors in various devices.

Temperature Sensitive Resistor

Temperature sensitive resistors, also known as thermistors, are resistors whose resistance value changes with temperature. They can be either positive temperature coefficient (PTC) or negative temperature coefficient (NTC) type, depending on the direction of the resistance change with temperature. NTC thermistors have a decreasing resistance value with increasing temperature, while PTC thermistors have an increasing resistance value with increasing temperature. Thermistors are widely used in temperature sensing and control applications, such as temperature measurement and compensation in electronic devices, and as over-temperature protection in power supplies and motors.

Light Dependent Resistor

Light dependent resistors, also known as photoresistors, are resistors whose resistance value changes with the amount of light they receive. They are made of a material, such as cadmium sulfide, that changes its electrical resistance in response to light. Photoresistors have a low resistance in darkness and a high resistance in bright light. They are widely used in light sensing applications, such as automatic light dimmers, light-controlled switches, and as light sensors in cameras and other devices.

What is Colour Coding of Resistors?

Resistors may not show their value on the outside, but you can figure out how much resistance they have based on their colour pattern. PTH (plated-through-hole) resistors have a color-coding system that makes circuits look really cool, and SMD (surface-mount-device) resistors have their own way of marking their values.

Here is a list of resistors' colour codes:

Colour Colour code
Black 0
Brown 1
Red 2
Orange 3
Yellow 4
Green 5
Blue 6
Violet 7
Grey 8
White 9

What is Tolerance in Resistors?

Following is a table with tolerance of resistor:

Colour Tolerance
Brown ±1%
Red ±2%
Gold ±5%
Silver ±10%

Resistors in Series

When the same amount of electricity flows through all of the resistors, we say that they are in series. In series, these resistors are linked from one end to the other. The total resistance of the circuit is equal to the sum of individual resistance values.

Resistors in Series Formula

Rtotal = R1 + R2 + R3 +……+Rn

Where,

• Rtotal is the sum of reciprocal of all the individual resistances

Resistors in Parallel

When the ends of two or more resistors are connected to the same two nodes, the resistors are said to be in parallel. When resistors are in parallel, the voltage at their ends is the same.

Resistors in Parallel Formula

1⁄R total = 1⁄R 1 + 1⁄R 2 + ..... + 1⁄R n

where, 1R total is the sum of all the individual resistances.

Applications of Resistor

Resistors are widely used in various electronic applications, including:

• Power Management: Resistor is used in power supplies, voltage dividers, and current limiting circuits to control the voltage and current levels in a circuit.
• Amplifiers: Resistor is used in amplifiers to adjust the gain and provide feedback in the circuit.
• Filtering: Resistor is used in filters to eliminate unwanted frequency components in a signal.
• Waveform Generation: Resistor is used in waveform generators to control the amplitude and frequency of the generated waveform.
• Sensing: Resistor is used in temperature, light, and position sensing applications to detect changes in environmental conditions.
• Protection: Resistor is used to protect sensitive electronic components from over-current and over-voltage conditions.
• Motor Control: Resistor is used in motor control applications to control the speed and direction of motors.
• Digital Circuits: Resistor is used in digital circuits to control the logic levels and provide pull-up or pull-down functions.

These are some of the main applications of resistors. They are widely used in various other applications as well, due to their simplicity, versatility, and low cost.

FAQs

What is a resistor?

A resistor is an electronic component that resists the flow of electrical current, thus limiting the current in a circuit. The resistance value of a resistor is measured in ohms and is used to control the amount of current in a circuit.

What is the SI unit of resistor?

The SI unit of resistance is the ohm (Ω).

Which type of resistor is used in photographic devices?

Photoresistors, also known as light dependent resistors, are commonly used in photographic devices such as cameras, light meters, and flash units. Photoresistors change their resistance value in response to light, making them useful for measuring and detecting changes in light intensity.

What are the two types of resistors?

Two types of resistors are:

• Linear resistor
• Non-linear resistor

What are various types of non-linear resistors?

Different types of non-linear resistors are:

• Thermisters
• Varisters
• Photo resistors