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What is the Resistance? Formula and Use of Resistors in Electrical Circuit

Hello Friends,

When you study the electrical devices or components, you should know the basics information about common electrical components.

One of the common components in electrical is Resistors. And its value is calculated in Resistance.

In this article, I explain-  ‘What is the Resistance?’,  formula and use of resistors in electric circuits.

What is the Resistance?


The property of the substances which opposes to the flowing of current or limiting current in the circuit is known as Resistance.

The high resistance provides the low current in the circuit and vice-versa.

Insulators usually have more resistance and good conductors have low resistance.

The resistance of the conductor depends on the following factor as given,

  • Length of the conductor
  • Nature of materials
  • The cross-section area of the conductor
  • Temperature of conductor

Symbol Representation of Resistance

Figure: Resistance (R)

Here, Resistance is signified by the ‘R’.

Measuring Instrument to Identify Resistance

It is measured in Ohmmeter 0r Digital Multimeter.

Unit: It  SI unit and CGS Unit are Ohm.

The formula to Calculate Resistance

Resistance = (Voltage /Current) 

Resistance=(Resistivity. Length)/Area 

Calculating the value of resistance by using the calculator –

The formula to Calculate Specific Resistance/Resistivity

ρ = (A*R/L)


R – Resistance of materials

ρ –  Resistivity or Specific resistance (In geek later is called Rho).

L – Length of conductor

A – Area of materials

Calculating the value of resistivity by using the calculator –

Schematic diagram of an electrical circuit:

Electrical Circuit with Resistance

In an electrical circuit, if the one amp current passes through the circuit which having voltage one volt, the resistance is calculated as one ohm.

Use of Resistors / Resistance in Electrical Circuit

Some of the common uses include, it is used to control the speed of the motors, to dim the lights, to control the loudness.

It is useful in many more different types of circuits.

What is the Resistor?


The components which provide a specific value of resistance in the electrical circuit is called a Resistor.

The resistor is a passive component as it can not operate without energy supply.

These components of substance are used to reduce the flowing current, control the circuit. It also maintains the voltage level or divide voltage in the circuit, adjusts the signal level.


If you look at the resistor image, there are 4 color bands pained on it. We can use these color bands to calculate the value of the resistor.

What are the different types of Resistors?

There are basically two types of the resistor as given below.

1. Fixed types of resistor

Example: carbon film, metal film, metal oxide film, carbon composition, wire wound, etc.

2. Variable types of resistor

Example: Potentiometer, Rheostat, Photoresistor, Thermistor, etc.

This is all about resistance, formula, and use of resistors. I hope you find this article helpful. If you have any questions, feel free to ask me in the comment section below.

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Happy Learning!

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