Resistor is one of most basic but important electronic passive components. It can be recognized by its distinct color bands printed over its cylindrical body.
The color bands are in fact the indications of the coded value of the particular resistor which can be determined by comparing and calculating these bands with the color code chart.
How to Use a Resistor:http://homemadecircuitsandschematics.blogspot.in/
Fundamentally resistors are used for controlling the flow of current in electronic circuits. These control is necessary otherwise the in surge of exceeding current can easily and instantly damage the various active components involved in the circuit.
They can be compared to watertaps in a pipeline. A water tap can be adjusted so that the flow of the water is produced at a desired slow rate. Resistor behave exactly the same way in electronic circuits by controling the flow of current at
To know how much current a particular resistor will control or allow to pass through it, we neeed to take the help of Ohm's law and formula, U = R.I
In the above equation, U is the source potential difference across the resistor and I is the unkown value we need to find.
As an example if U = 12 V, and R = 1000 Ohms then I becomes = 0.012 Amps or 12 mA. It means this resistor will allow only a current of 12 mA to pass through it.
In this way by calculating the currents we can estimate which resistor might be required for a particular application in an electronic circuit