RESISTORS OVERVIEW - what is resistor ? - what are the types of resistors ? - what are the material used in resistors making ?

Resistors are electronic elements that are used to limit the amount of current or voltage in a voltage.

In general, resistors classified as fixed resistors and variable resistors, in which resistor values remain fixed at a constant value are known as fixed resistors. Variable resistors are classified into rheostats and potentiometers, which resistors are used in circuits where we want current and voltage to be controlled or regulated.

FIXED RESISTORS

Wire wound resistors

Wire wound resistors consist of a former made up of an insulating material like ceramic or plastic. The former is cylindrical or rectangular in shape. These resistors are available from 0.001Ω to several tens of kilo ohm. 

             

              They can be used in high-temperature situations but are very large in size and weight. They are capable of carrying extremely large currents but in some situations wire can break, leading to the breakdown of the circuit. These types of resistors were very costly.

Carbon resistors

  These resistors are made of carbon which acts as a conductor. The two types of resistors available one is carbon film resistors and another one is carbon composition resistors. 

        

     Thin film resistors are manufactured by depositing a thin film of carbon on a ceramic substrate. Thick films greater than 5μm in thickness. Thick films are manufactured by gold, platinum and palladium.

    Carbon composition resistors have two basic types one slug type and another one is glass filament type.  this type of resistor is made of carbon granules mixed with an organic binder and moulded into a pellet shape.

         

     Carbon film resistors are available in miniature sizes and have a good high frequency. But they are vulnerable to mechanical shocks and chemically reactive.

                             VARIABLE RESISTORS

Rheostats 

     Usually, variable resistors are used in circuits where we want current and voltage to be controlled or regulated. Rheostats can handle small and large power alike. They have a large current carrying capacity. But these resistors' values greater than about 10 kΩ,  they are costly, bulky and large weight.

Potentiometers

   Potentiometers also have variable resistances. They are made of carbon or wire. Potentiometers are smaller than rheostats. Carbon resistors are available from MΩ. Wire wounds are available up to 100 kΩ. These are limited by large tolerance values.