Resistors are composed of highly resistive material to mitigate the flow of current or drop the voltage on purpose. These are passive circuit elements and dissipate electrical energy. During the flow of current, the electron jumps from one atom to another atom, collisions occur and kinetic energy converts to potential energy in the form of heat. Thus the resistors are energy converter from electrical energy to heat. Moreover, there are two types of resistors in electrical engineering; fixed resistors and variable resistors which I will explain later.
The flow of charge through any material encounters opposition from that material. This opposition is resistance. This opposition is way much similar to a mechanical fraction. In electrical engineering, the resistance is represented by R and the unit of resistance is “Ohm”. The resistance of a material is dependent upon the length, cross-section area, and nature of the material.
Resistance, current, and voltage are very closely related to each other by Ohm’s law. According to the ohm law, current increases as we increase the voltage across the resistor. Alternatively, the statement means that the current and voltage ratio remains constant. This ratio is resistance.
Types of resistors :
There are a number of types of resistors because of different electrical or physical properties. Which makes them suitable for specific applications. The resistors are mainly divided into two types, first Fixed Resistors and second, variable resistors. In Fixed resistors, the electrical resistance of the resistor the remains same while in variable resistor it does change with some physical variable.
These widely used resistors are a having fixed resistance value defined at the time of manufacturing. Their resistance value is either printed over the resistor or color-coded over them. Following are the types of fixed resistors.
Carbon Composition Resistors :
These resistors were used commonly in past but are rarely used nowadays. Because of the use of a large negative temperature coefficient and some erotic irreversible changes. They are formed from carbon grains with the help of binding aid, which generates noise during current flow.
Carbon Film Resistors :
Carbon film resistors are formed by the deposition of carbon material into an insulating substrate. Because of the absence of binding aid, as compared to carbon composition these resistors produce less noise.
Metal Oxide film resistors :
Instead of carbon, the metal oxide resistor uses metal oxide deposition on to a ceramic rod. The thickness of the metal oxide film can adjust the resistance value. In some variations, some metals such as nickel alloys can be used instead of metal oxide as an upper layer.
Wire Wound Resistors :
By winding a metal wire i.e. Nichrome around insulators like ceramic, wire wound resistors are produced. The terminals are soldered with metallic caps and then protected with a layer of paints or molded plastic to withstand high temperatures. Because of being a coil, the wire wound resistors are having more inductance but they can be compensated using two coils in reverse directions.
Thin Film Resistors :
Thin-film resistors are used most widely nowadays with compact size and low tolerance. They are mostly Surface Mount Types of resistors. These resistors are constructed from a ceramic substrate and deposition of metal oxide onto it. Where the thickness of the film determines the resistance value.
Printed Carbon Resistors :
Resistors that can be printed onto a PCB board from carbon material are printed carbon resistors. It has a high tolerance. But the practice is very common in hybrid PCB manufacturing modules. Typical usage of the printed carbon resistor may be pull-up resistors.
Variable Resistors :
Variable resistors are those whose resistance value can be changed by adjusting some knob. These resistors are used rarely because of moving parts and uncertainty.
It is a three-terminal device containing the main resistance wire and a slider that slides above it. By adjusting the position of the slider, a portion of the main resistance can be utilized.
A two-terminal fixed tapping device, whose resistance can vary by changing the tap position. ala lowing a smaller or larger part of the resistor can be used.