Resistors are used in an electronic circuit to resist the flow of the electric current. The symbol of resistor is as follows.
The simpliest circuit with a resistor can be shown as follows:
In this circuit electric current is flowing from the positive terminal of the bettery to the negetive terminal through the resistor. During passing the resistor the carrier faces resistance and some to kinetic energy of the carrier converts to heat. Therefore, work is done by the resistor and it can be considered as a load for the battery/power source.
Resistance of a resistor is measured by the unit ohm (Ω). In a circuit, usually the value of resistors differs from 0.01 Ω to 100 MΩ. [1MΩ = 1000 kΩ = 1000000 Ω ]
If you are an electronic hobbyst and only want to make projects by only copying from the diagrams, you dont need to know the calculations related resistance in details. However, if you want to design circuits or modify for your own interest you should understand the various functionallity of resistors and their relationship with elcetric current and potential difference. I discussed these advanced learnings in intermediate tutorials.
There are several types of resistors available for various purposes. I will discuss about them in relevent articles when needed. There are different types of resistors used in electronic circuits and among them carbon film resistors are most commons. These resistors look like the below picture.
The wattage of resistors is an important parameters for desining a circuit. Resistor with comparatively low values sometimes generate excesive heat. In that case, resistors with high wattage is needed. Generally, resistors of 1/10, 1/8, 1/4, 1/2, 1, 2, 5, 10 watts are used in the circuits. Among these, 1/4 is the most common wattage rating of resistors.