There are 6 types of resistor depending upon their construction, power dissipation capacities and tolerance of the value. Such as (Carbon Composition Resistor, Metal Film Resistor, Carbon Film Resistor, Non Linear Resistor, Varistor, and Thermistor). Before explaining each types of resistor i will tell you definition of resistor. Let’s see below.
The unit of resistance is ohm and it is represented as Ω. When one volt potential difference is applied across a resistor and for that one ampere of current flows through it, the resistance of the resistor is said to be one Ω. Resistor is one of the most essential passive elements in electrical and electronics engineering.
Table of Contents
- 1 Types of Resistor Carbon, Composition, Film and Non Linear
Types of Resistor Carbon, Composition, Film and Non Linear
It is some time required to introduce electrical resistance in different circuit to limit the current through it. Resistor is an element of circuit which does the same. Such as series connected resistor limits the current flowing through the light emitting diode (LED).
In addition to that resistors serve many other purposes in electrical and electronic applications. The most essential requirement of a resistor is that its value of electrical resistance should not vary with temperature for a wide range.
That means resistance variation with temperature must be as minimal as possible for a wide range of temperature. In other word the temperature coefficient of resistance of must be minimum for the materials by which a resistor is made of. Here we will discuss mainly about types of resistor.
Carbon Composition Resistor
These types of resistor are very commonly used low cost resistor. The construction of carbon composition resistor is very simple. It is also commonly referred as carbon resistor. It is mainly made of carbon clay composition covered with a plastic case.
The lead of the resistor is made of tinned copper. The main advantages of these resistors are that they are easily available in local market in very low cost and they are very durable too. But the main disadvantage is that they are very much temperature sensitive.
These resistors are available in wide range of values. It is available in as low as 1 Ω value and it is also available in as high as 22 Mega Ω value.
The tolerance range in resistance of carbon composition resistor is of ± 5 to ± 20 %. Such resistor has a tendency of electric noise due to passage of electrical current from one carbon particle to other.
Where low cost is the main criteria of designing a circuit rather than it’s performance, these resistors are normally used.
These carbon resistors are provided with different colored band on their cylindrical body. These color bands are code for the resistance values of carbon composition resistor along with their tolerance range.
Metal Film Resistor and Carbon Film Resistor
Basic structure of this type of resistor is constructed by means of film deposition technique of deposition a thick film of resistible material such as pure carbon or metal on to an insulating core.
The desired value of resistance of metal film resistor or carbon film resistor can easily be obtained by either trimming the layer of thickness or by cutting helical grooves of suitable pitch along its length.
That means for different resistance values, the length and depth of the helical grooves is maintained accordingly.
Metallic contact cap is fitted at both ends of the resistor. The caps must be in contact with resistible film or helical grooves. The lead wires are welded to these end caps.
Metal Film Resistor or Carbon Film Resistor can be made up to a value of 10,000 MΩ and size of this type of resistor is much smaller than wire wound resistor resistor.
Because of their constructional features these resistor are fully non – inductive. The accuracy level of metal film resistor can be of order ± 1 % and they are suitable for high grade applications.
Carbon film resistor givers lower tolerances and smaller values of electrical resistance than those available with metal film. However the carbon film posses a mildly negative temperature coefficient of resistance which is very useful for certain electronic circuit.
This is a special resistor that is used in electrical circuit. The word means that it is thermal resistor. Its resistance value changes with the change in the temperature value.
Most of the thermistors have the negative temperature coefficient which means its resistance will fall down when the temperature value increases. The temperature coefficient may be positive as well.
It is constructed by the use of various metals such as nickel, cobalt, copper etc. Also it can be prepared from the semiconductor devices as well. We can obtain a resistance upto a few mega ohms value.
They are used to detect the small temperature changes, when there is a temperature change, however small, there will be a large change in the value of the resistance. Also they are used for voltage stabilization and remote sensing.
Non Linear Resistor
They are also known as varistors. They are popular for having the non linear V-I characteristics curve. That is its resistance is not uniform and it does not obey OHM’s law. They are made of materials such as silicon carbides, zinc oxide.
They are of three types:
- Silicon carbide disc type varistor.
- Silicon carbide rod type varistor.
- Zinc oxide type varistor.
Light Dependent Resistor
As the name suggests its resistance value depends on the intensity of light falling on it. This is made of cadmium sulfide containing a very small number of electrons when not illuminated.
When light ray of a particular intensity falls on it electrons are ejected and hence the conductivity of it increases. That is it offers low resistance when light falls on it and offers high resistance in the dark or no light condition.
They are only light dependent up to a wavelength of 680 nm. Mathematically we can say that, R = KE-α Where, K and α are constant. R is the resistance value in ohm. E is the intensity of illumination in lux.
Types of Resistor Carbon, Composition, Film and Non Linear Conclusion
After going through the above types of resistor we can now establish how resistor works . I hope you enjoy when reading this article, thank you.