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BASIC UNDERSTANDING OF RESISTORS

Updated: Feb 2

Building the circuit requires information on various components like Resistors, Inductors, Capacitors, Battery sources, connecting wires and more. The Resistor is one of the fundamental components of the circuit. Playing a vital role as a passive circuit component. Let us know some basic details about the resistor.


What is resistor?


A Resistor is a passive electrical component with two terminals that are used to limit or regulate the flow of electric current in electrical circuits.

Resistor
Resistor

Mainly resistors reduce the current flow and lower the voltage in a particular portion of the circuit. It is made up of copper wires coiled around a ceramic rod and the outer part of the resistor is covered with an insulating paint, also resistor is an essential circuit component.


S.I. Unit of Resistor is Ohm(Ω).


Resistor Symbol



What is Resistance?


Based on Ohm’s law named after German physicist Georg Simon Ohm, the resistance is defined as:


As per Ohm’s Law, the voltage V across a resistor is directly proportional to the current I, flowing through it. Here, the resistance R is constantly proportional. Therefore,

Ohm's law

Working Principle of Resistor


In the process of impeding the flow of current and reducing voltage, a resistor absorbs electrical energy, which dissipates as heat. In electronic circuits, the heat dissipation is typically a fraction of a watt.


Ohm’s law states that if I will is the current flowing through the resistor in amperes, and Resistance R in ohms, then V is the voltage drop that is imposed by the resistor (It is the difference in electrical potential between the two contacts.)

V with I and R relation

Another way of saying, the 1-ohm resistor will allow a current of 1 amp when there is a capacity difference between the ends of the resistor of 1 volt.


If Power P in watts is dissipated by the resistor, then In a DC circuit:

Power dissipation of resistor with V and I

By substitution of Ohm’s law, we can express power in watts in terms of voltage V and resistance R will be:

Power dissipation of resistor with ohm's law

Also express power in watts, in terms of voltage V and resistance R is:

Power dissipation of resistor

When you are unsure of the voltage drop or current, respectively, you can use these alternate formulae. When employing alternating current, roughly same equations hold true, but the resistor's role in terms of power will be more complicated.


Resistor Series and Parallel Circuits


In some cases, an electrical circuit could have at least two resistors. They can be connected in series and parallel.


The resistors, when connected in the series, are known as a series connection, and the current flowing through the series connection will be the same. The amount of the voltage across every resistor will be equivalent to the voltage across the resistors. Suppose the three resistors R1, R2 and R3 are connected in series ways then the total resistance total R, will be calculated and shown series circuit component as below:

series connection
series connection
Total series resistor formula

If the resistors are connected in parallel is known as a parallel connection. Here, the voltage applied across every component remains the same. The amount of the current across each resistor is equivalent to the currents across the series. Suppose the three resistors R1, R2 and R3 are connected in parallel ways then the total resistance total R, will be calculated and shown parallel circuit component as below:

Parallel Connection
Parallel Connection
Total parallel resistor formula

Power Dissipated in a Resistor


The below equation will give you the value of the power P, dissipation through a resistor will be given as:

Power dissipation of resistor

Types of Resistors -


1. Linear Resistor

Linear resistors have values that vary when the temperature and voltage applied to them change. There are two types of linear resistors which are below


Fixed resistors -

Fixed resistors are those whose value will be fixed, and that cannot be changed. The different types of fixed resistors are:

  1. Resistors with a carbon content.

  2. Wire-wound resistors are a form of wound resistors.

  3. Thin-film resistors.

  4. Resistors with a thick film.


Variable resistors -

Variable resistors are those whose values will be specific value and the values can be changed with the help of a dial, knob, and screw. The various types of variable resistors are:

  1. Potentiometers.

  2. Rheostats.

  3. Trimmers.


2. Non-Linear resistor

Resistor values vary with temperature and applied voltage, hence Ohm's law does not apply to them. The following are the types of non-linear resistors:

  • Thermistors.

  • Varistors.

  • Photo resistors.


Resistor color code


The electrical resistance is represented by color bands printed on them. providing an easy means of identification for this vital circuit component.



Reading color code of the resistor value:


  • Hold the resistor such that the tolerance band is to your right. The tolerance band is typically gold or silver and is placed away from the other bands.

  • Write down all the band colors, starting from your left, in the correct order.

  • Then, use the above table to see which digits they represent.

  • The band just close to the tolerance band is the multiplier band.

  • Above shown color-coded resistor value will be

Color code value of the resistor

Application and uses of resistors


  • High-frequency instruments employ resistors.

  • Circuits for power control employ resistors.

  • Electricity supply that uses DC electricity uses resistors.

  • Filter circuit networks employ resistors.

  • Digital multimeters, oscillators, amplifiers, and communications all employ resistors.

  • Transistors, modulators, and demodulators all need resistors.

  • Voltage regulators and medical equipment both require resistors.

  • Feedback amplifiers employ resistors as circuit components.


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