Basics on Resistors

Resistors may be the first discrete component that we are learning while entering in to the world of Electronics. In this post we are discussing some of the important things to know about resistors in an application oriented perspective.

What is a Resistor?

  • A component which resists the flow of electric current (electrons). It has a linear V-I Characteristics and thus satisfy ohms law.

How to find the value of a resistor?

  • Using Resistor Colour Coding
  • Using a Multimeter in resistance mode

(There are lot many other methods but these are the simplest way)

Different Types

  • Fixed value resistors & variable resistors ( potentiomenter, trimmers, preset etc)
  • Types based on the make (Carbon Resistors, Film Resistors(Carbon, Metal), Wirewound, )

Considerations while selecting a resistor for your circuit

Choosing a resistor for your circuit is not just about the designed value. There are few other important consideration.

  • Tolerance of the Resistor: Tolerance is the variation from the given resistor value. if your design has to be precise, accurate and has hard constrains, using a resistor with low tolerance would be good.
  • Power Rating of the Resistor: Make sure that you are using a resistor with correct power rating, other wise it will heat up excessively and burned off later. Assume you are using 1kOhm resistor and, a current of 0.01A is flowing through it. Then the power dissipation of the resistor would be I*I*R= 0.01*0.01*1k =0.1Watts. Then you can use a 0.25W resistor. Now assume a current of  0.02A flows through, then after calculation, we will get the power dissipation as 0.4W. Then you not be able to use 0.25W resistor, instead you have to choose 0.5W resistor.
  • Operational Temperature: Resistance varies as temperature varies. So, while we select a resistor, we have to refer it’s typical operational temperature range.

About author: Mr. Thomas Sabu is an electronics enthusiast and currently leading the R&D activities of Neo Green Labs.

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