# What Is a Fixed Resistor

Fixed resistors are a type of electronic component that plays a crucial role in electronic circuits. They are passive components that resist the flow of current and have a fixed resistance value that cannot be adjusted. In this article, we will explore what is a fixed resistor, how they work, their different types, and their applications.

## What is a Fixed Resistor?

A fixed resistor is known as an electronic component that opposes the flow of electric current. They are passive components, meaning they do not require an external power source to operate. Fixed resistors are called such because they have a fixed resistance value that cannot be adjusted. The resistance value is determined by the material and construction of the resistor.

## How Fixed Resistors Work:

Fixed resistors work by converting electrical energy into heat. They resist current flow and reduce the amount of current passing through a circuit. The amount of resistance in a fixed resistor is measured in ohms. There is Ohm’s law that fixed resistors follow, the law states that the current through a conductor between two points is directly proportional to the voltage across the two points.

Fixed resistors are passive components that regulate the flow of electric current in electronic circuits. They work by converting electrical energy into heat, which reduces the amount of current passing through a circuit. In this section, we will take a closer look at how fixed resistors work.

### i. The Basics:

Fixed resistors are made of a resistive material that opposes the flow of electric current. When current passes through the resistor, it encounters resistance, which reduces the amount of current flowing through the circuit. The amount of resistance in a fixed resistor is measured in ohms and is determined by the material and construction of the resistor.

### ii. Heat Generation:

As current passes through the resistor, it generates heat. The heat generated is proportional to the amount of current passing through the resistor and the resistance value of the resistor. The heat generated can be significant in high-power circuits and can cause the resistor to overheat if the power rating of the resistor is exceeded.

### iii. Temperature Coefficient:

The resistance of a fixed resistor can vary with changes in temperature. The temperature coefficient of a resistor measures the rate at which the resistance value changes with changes in temperature. Different types of resistors have different temperature coefficients, which can affect their performance in high-temperature environments.

### iv. Connecting Fixed Resistors in Series and Parallel

Fixed resistors can be connected in series or parallel to achieve specific resistance values in a circuit. When resistors are connected in series, their total resistance is the sum of their individual resistance values.

When resistors are connected in parallel, their total resistance is calculated using the formula-

Rtotal = 1/(1/R1 + 1/R2 + 1/R3…).

Knowing how to connect fixed resistors in series or parallel is essential when designing and troubleshooting electronic circuits.

## Types of Fixed Resistors:

There are different types of fixed resistors, including carbon composition, film, wire-wound, and surface mount resistors. Each type has its unique features, size, power rating, and tolerance. In this section, we will discuss the four main types of fixed resistors and their characteristics.

### i. Carbon Composition Resistors:

Carbon composition resistors are the oldest type of fixed resistor and are still used in some applications. They are made of a mixture of carbon and an insulating binder that is shaped into a cylindrical or rectangular form. Carbon composition resistors have a low tolerance value, meaning their resistance value can vary up to 20% from their nominal value. They are typically used in low-power circuits or as current limiters.

### ii. Film Resistors:

Film resistors are made of a thin layer of a metal film deposited on a ceramic substrate. They have a high precision value and are commonly used in precision circuits. Film resistors are available in both axial and surface mount packages and have a tolerance value ranging from 1% to 5%. They are widely used in audio equipment, instrumentation, and other high-precision applications.

### iii. Wirewound Resistors:

Wirewound resistors are constructed by winding a resistance wire around a fiberglass or ceramic core. They have a high power rating and are ideal for circuits with high power requirements. Wirewound resistors are commonly used in power supplies, motor control, and other applications that require high-power handling. They have a low tolerance value and are available in both axial and surface mount packages.

### iv. Surface Mount Resistors:

Surface mount resistors are compact and are commonly used in portable electronic devices. They are made of a thin film of metal deposited on a ceramic substrate and are available in different sizes and tolerance values. Surface mount resistors are designed for automated assembly and are often used in high-volume production applications.

In summary, fixed resistors are available in different types and are used in various electronic devices and applications. Each type of fixed resistor has unique features, size, power rating, and tolerance. Knowing the characteristics of each type of fixed resistor is essential when designing and troubleshooting electronic circuits.

## Resistance Tolerance and Power Rating

The resistance tolerance and power rating of a fixed resistor is two critical parameters that determine its performance in a circuit. The resistance tolerance of a resistor means the maximum deviation of the resistor’s actual resistance value from the nominal resistance value. A resistor’s power rating means the maximum amount of power that without overheating a resistor can safely dissipate. Knowing the resistance tolerance and power rating of a resistor is essential when selecting the appropriate resistor for a specific application.

## Applications of Fixed Resistors:

Fixed resistors are used in a wide range of electronic devices and applications. They are essential components in power supplies, audio equipment, lighting, and more. They help regulate and control the flow of current and voltage in electronic circuits. Fixed resistors are also used in resistive networks and voltage dividers to provide specific voltage levels to other components.

Fixed resistors have various applications in electronic circuits, ranging from current limiting to voltage regulation. In this section, we will discuss some of the common applications of fixed resistors.

### i. Voltage Divider:

Fixed resistors are commonly used in voltage dividers, which are circuits that divide a voltage into smaller parts. Voltage dividers are used in various applications, including analog-to-digital converters, instrumentation amplifiers, and audio equipment. The output voltage of a voltage divider depends on the ratio of the resistance values of the resistors used in the circuit.

### ii. Current Limiting:

Fixed resistors are used as current limiters in electronic circuits to prevent damage to sensitive components. A current-limiting resistor is placed in series with a component to limit the amount of current flowing through it. For example, a LED is often protected by a current-limiting resistor to prevent it from burning out due to excessive current.

### iii. Pulse-Width Modulation:

Fixed resistors are also used in pulse-width modulation circuits, which are used to control the speed of motors and other devices. Pulse-width modulation circuits work by rapidly switching a fixed voltage on and off, with the amount of time the voltage is on relative to the time it is off controlling the speed of the motor. Fixed resistors are used in these circuits to set the duty cycle of the pulse width modulation.

### iv. Filtering and Biasing:

Fixed resistors are used in filtering and biasing circuits, which are used to remove unwanted noise or to establish a desired voltage level. For example, a voltage divider circuit can be used to bias the input of a transistor to a desired voltage level.

### v. Temperature Compensation:

Fixed resistors are used in temperature compensation circuits to reduce the effect of temperature changes on the performance of a circuit. Temperature compensation circuits use a combination of resistors and thermistors, which are resistors that change their resistance with changes in temperature, to maintain a consistent output voltage or current regardless of temperature changes.

In summary, Fixed resistors are an essential component in electronic circuits and have various applications ranging from voltage dividers to current limiting. They are used in many different types of electronic devices and are available in various sizes, power ratings, and tolerances. Understanding the different applications of fixed resistors is essential for designing and troubleshooting electronic circuits.