Member • Jun 17, 2014
Basic Electronics Part_II: Resitors
Resistors
1. Its a electronic or electrical device that resist the flow of elctrons through the device.
2. They are passive devices that is they have no source of power or amplification but it attenuates the voltage or current signal passing through them.
3. Because of this attenuation the electrical energy is lost in the form of heat as the resistor resist the flow of electrons .
4. Most of the resistors are linear devices and obeys ohms law.
5. They are represented by the zig-zag line. Its unit is Ohm.(Ω)
6. Some important characteristics of resistors: temperature coefficient, voltage coeffcient, noise, frequency response, power, temperature rating, physical size and realibility.
Applications :
1. Used in amplifiers as load for active devices, and as feedback elements.
2. When used along with capacitors, they establish time constant and are used as filters. Helpful in setting operating point and signal levels.
3. In radio frequency circuiuts, they are used as coils in the form of inductors.
4. In logic circuits they are use as bus and line terminators. They are also used as pull-up and pull-down resistors.
Types of resistors
Based on the mode of operation they are classified into two types
1. Fixed point
2. Variable resisters.
1. Fixed point:
· They have only one single value of resistor associated with it.
· They are further divided based on the type of material used for it such as metal wound, wire wound, carbon composition resistors.
Colour coding in resistors.
To indicate the value of resistors this type of colour coding is used. This is done because the size of the resistor is so very small to write its value on it.
There are four bands into it.
Value of resistors is calculated from left till right.
Digit, digit, multiplier= colour , colour×10colour(Ω)
=4,7,103 =47000 Ω
Thus here, the valure of resistor will be:
Clue to remember this colour code:
Bright (black)
Boys (brown)
Rave (red)
Over (orange)
Young (yellow)
Girls (green)
But (blue)
Veto (violet)
Gets (grey)
wed. (white)
2. Variable Resistors:
Here the resistance can be adjusted while it is in connection with the circuit.they usually have three leads, two of them are fixed and one is variable. If contacts are made to only two leads then it is called as a rheostat. If all the three contacts are employed then it is called as potentiometer.