Electronics And Electrical Tutorials

Published by:

Renji Elsa Jacob, M-Tech in Electrical & Electronics Engineering

Electronic Components- Resistors

In Electronics, we have many components that assist in different purposes. Various elements are used in many types of circuits depending on the applications. In the structure of electronic circuits, several basic electronic components are used.

Circuit designs are never complete or it does not work well, without these components. These components consist of resistors, diodes, capacitors, integrated circuits, etc. Some of these components that are soldered to circuit boards consist of two or more terminals while some may be packaged types like integrated circuits in which different semiconductor devices are integrated.

Definition: Electronic components are the elements of a circuit that helps in its working.

They are the basic building blocks of an electronic circuit or system or device which controls the flow of electrons in an electronic system or electronic circuit. Electronic components are very small. So, it is easy to carry them from one place to another place. The cost of electronic components is also low. When we connect a group of electronic components in an electronic board such as a printed circuit board (PCB), a useful electronic circuit is formed. Each electronic component in a circuit performs a specific task.

Classification of Electronic Components

Electronic components can be classified into two types i.e. Active Components and Passive Components.

Active Components	Passive Components
The devices that depend on energy source and can introduce power into the circuit. It can control the flow of electrons through them. For Example, transistors, diodes, ICs, Power supplies, etc	The devices cannot control the flow of current through them i.e. they cannot introduce energy into the circuit but can increase or decrease voltage and current. For Example, resistors, capacitors, inductors, and transformers.

Passive Electronic Components

These components maintain or store energy in the form of current or voltages. Let us discuss the components here:

Resistors

It is the most commonly used components in electronic circuits and devices. A resistor is usually used to maintain specified values of voltage and current in an electronic circuit. The resistor works based on the principle of ohm’s law which states that the voltage across the terminals of the resistor is directly proportional to the current flowing through it.

So we can that a resistor is a two-terminal passive electronic component which used to oppose the current.

Resistors can be represented by the following symbols:

The resistor has a property called resistance. Resistance is a property of opposing the flow of electron in a conductor or semiconductor. The units of resistance are ohms (Ω), omega.

The formula of resistance:

R=V/I

Where V is Voltage and I is Current. To manufacture the resistor with all the values is difficult, so some values are chosen and only those are manufactured. So these are called Preferred-Value. So for practical use, we select resistors with approximate values to match the required applications.

Characteristics of Resistors

1. Power Rating: Power rating is the amount of power consumed by the resistor. It is highly recommended to use a resistor with a power rating value over what is exactly required.
2. Noise: It is important to have low noise properties for some resistors. Noise properties are mostly dependent on 3 parameters: resistance, temperature, and bandwidth.
3. Tolerance: Tolerance, an important factor is the range of value up to which a resistor can resist without getting destroyed.
4. Voltage rating: The voltage rating of a certain circuit can be securely adjusted through the application of resistance.
5. Temperature rating: Temperature rating is the range of the device where it can operate normally. Exceeding the limit will cause the resistor to be damaged or burnt.
6. Stability: Stability is defined as the repeatability of the resistance of a resistor when measured at a situation temperature and subjected to various operating and environmental conditions.
7. Frequency response: The frequency response is simply the change in impedance. The different function of the circuit changes the value of impedance

Color Coding

The process used to determine the value of resistance of a resistor is called color-coding.

4 Band Resistor

A resistor has 4 color bands where each band represented a particular value.

• The first two colors represent the first and second digit of the value
• The third color band represents the number of zeros to be added.
• The fourth band represents the tolerance value.

5 Band Resistor

• The first three colors represent the first, second, third digit of the value
• The fourth color band represents the number of zeros to be added.
• The Fifth band represents the tolerance value.

Problem

1. Find the resistance value in ohms and the percent tolerance for each of the color coded resistors.

a)

b)

• First and is Brown  = 1, Second band is green = 5, Third Band is red = 2 zeros, Fourth Band is Gold = ±5% Tolerance

R = 1500Ω ± 5%

• First band is orange  = 3, Second band is orange  = 3, Third Band is white = 9, Fourth Band is Black = 0, and Fifth Band is Brown = ±1% Tolerance

R = 339 Ω ±1 %