Introduction: What Is a Resistor | Basics

If you have ever built a circuit, then you might have come across this component, this is a resistor. So how does it works let’s find it out!

Step 1: Watch the Video !

I have made video on Youtube which is much easier to understand check it out !

Step 2: Basic Introduction

Resistor is an electrical component that resists rate of flow of current and unit of resistor is Ohms.

it is represented by two symbols show above.

Ohm's law
The current I is equal to the voltage V divided by the resistance R

also represented by V=I*R

Step 3: Resistors in Series and Parallel.

Resistors in series

The equivalent resistance of resistors in series is the sum of the resistance values:
Req= R1+ R2+ R3+...

Therefore equivalent resistance increases

Resistors in parallel

The equivalent resistance of resistors in parallel is given by:


Therefore equivalent resistance decreases

Step 4: Voltage Drop

This happens when resistors are connected in series and the drop in the voltage can be calculated using the formula


Step 5: Power Rating of Resistor

There are various types of resistor such as Shunt, Power, Variable etc.

But most importantly Power rating is a crucial factor while designing the circuit or else You can see what can happen in the circuit in this Video.

Step 6: Application

Lets say we want to power a LED which requires 3V and 20 mA to operate and we want to power it using 9V battery, then we need a resistor otherwise LED will get damaged instantly because of excess current. The value of the resistance can be calculated using the ohms law, which says voltage equal to current times resistance. So our voltage is 9V and current is 20mA so resistance value comes out to be 450 ohms but I have 1k ohm resistors so I will add 2 of them in parallel so equivalent resistance becomes 500 Ohms.

Step 7: Thank You

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NagelmaierP (author)2017-09-19

In step 6 you say that the current is 20mAH, but this is a capacity, it should say 20mA.
Also you would not use 9V in the calculation, but 9V minus the working voltage of the LED, so 6V.

Anshu AR (author)2017-09-13

Nice instructable!

Just a small question off the topic, Whats that multimeter you are using?

I mean I have to buy one. So is that a reliable one?

gm280 (author)2017-09-13

When you really understand electronics really well, it is amazing how many components you can literally make with household items. I love making circuits for my needs.

michaelthehutt (author)2017-09-13

nitpick: for resistors in parallel, you have "Req=(1/R1)+(1/R2)+(1/R3)+...", but I believe that should be "1/Req = (1/R1)+(1/R2)+(1/R3)+..." (ie - invert the sum of the inverted resistance values).

Nematic! (author)michaelthehutt2017-09-13

Updated !
Thanks mate that was a typo :)

About This Instructable




Bio: Hi, I'm Nemeen !, Electronic and robotics enthusiastic. This is my channel 'Nematic !' I will be uploading on and about awesome Electronics Tutorials, Projects and ... More »
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