Resistors are those tiny little electronics components which opposes the flow of electric current. Whenever we try to build a small circuit, if a resistor is added into that circuit, the job of resistor is to resist (or oppose) the current flow.
The value of resistance offered by a resistor never changes. Resistors are passive components means it doesn’t matter in which direction you connect it in a circuit, it will work the same way. By using resistors we can limit the current flowing through a circuit. As seen in previous tutorial, resistance offered by a resistor is measured in Ohms (capital omega symbol Ω)
When drawing circuit on a paper, resistor is shown by a specific symbol as shown below
Where R1 or R2 shows which no of resistor is this in the circuit and the 1KΩ or 47KΩ shows the value of resistance offered by this component.
Resistor Value
The resistors offer electrical resistance which can be measured on Ohms. We can measure the exact resistance of a resistor by making use of multi meter, but for quickly knowing value of any given resistor, we can look at the color bands printed on resistor body. Look at below picture
This above picture explains how value of a resistor is calculated. Every color band printed on resistor has a specific number associated with it as shown in below chart. The first color band (its respective number) is the first number in value of resistor, second color band (its respective number) is the tenth place of resistor value, and the third band (its number off course) indicates order of 10 with which the value will be multiplied to get the final value. Here’s the resistor color coding chart
You can also use below mentioned calculator to find out your resistor value
http://www.dannyg.com/examples/res2/resistor.htm
Sizes
Resistors come in various sizes and different types. The sizes of resistors are usually dependent upon how much power it can handle (remember, we have big power point in home for Fridge, Geyser, AC etc… same way!!!) a big sized resistor is used to handle big amount of electric power. The resistor value has nothing to do with the power consumption and both are independent properties. Look at the picture below for various resistor sizes
Above picture shows three different resistors sizes. All three of them have different power ratings and usually, the bigger one is with the large power rating and small one is with smaller power rating. Look at below picture for a visualization of resistor sizes
As you see in above picture, it’s fairly simple to notice that as the wattage increases, size of resistor increases.
Variable Resistors
Generally the types of resistors are based on the material they use. Some resistors are only made up of carbon, some utilizes a special type metal offering some fixed resistance and so on. Most common ones we see and use utilize a carbon film and hence called as Carbon film resistor or CFR.
Then comes variable resistors, these are having three points, two points, which offer a fixed resistance and one variable point which can float between these two points. If these are such that can be mounted on bread board, its called as preset, and if its like a simple knob which can be rotated (just like volume control of a player) then its Called as potentiometers, or simply as POT.
The above figure shows Presets and below figure shows how a pot looks like, note, they all are 3-point components.
