All resistors are classified into two major classes. A fixed resistor exhibits essentially constant value of resistance, whereas a variable resistor exhibits variable resistance. In this post, you'll learn about the difference between fixed and variable resistors.
Let's start with the summarized table of data:
Let's start with the summarized table of data:
Fixed Resistors
Carbon Resistors
Carbon type resistor is a fixed resistor which contains an insulating body surrounding the carbon. The value of resistance is varied by changing the amount of carbon, a lower proportion of carbon results in higher resistance and vice verse. Carbon resistors are cheaper as well as their manufacturing process is very easy.
Features of Carbon Resistors
Feature | Detail |
---|---|
Designed for Resistance | 1 Ω-100 MΩ |
Designed for Power | 0.125 W - 2 W |
Carbon film
A thin carbon film surrounds the ceramic carrier acting as a resistive material.
Features of Carbon Film Resistors
Feature | Detail |
---|---|
Designed for Resistance | 1 Ω-10 GΩ |
Designed for Power | 0.625 W - 2 W |
Tolerence value | 2% / 5% / 10% / 20% |
Practical applications | HV applications, X-rays, Laser |
Metal film
They comprise a thin metallic film surrounding the resistive element. They are reliable and are have excellent tolerance values. However, they are expensive.
Features of Metal Film Resistors
Feature | Detail |
---|---|
Designed for Resistance | 1 Ω-10 MΩ |
Designed for Power | 35 W |
Tolerence value | 0.1% / 0.25% / 0.5% / 1% / 2% |
Practical applications | Low noise applications, X-rays, Laser, Bridges such as Wein, Wheatstone |
Variable Resistors
Potentiometer and Rheostat
The class of variable resistors whose value of resistance can be varied by using a circular knob. Although both potentiometer and rheostat are same devices, the names potentiometer is given to configuration when a variable resistor is set to provide a variable voltage on the output. Whereas the name rheostat is given to the device which provides variable current in the circuit.
Potentiometer | Rheostat |
---|---|
Provides variable voltage | Provides variable current |
Thermistor
The thermistor is a variable resistor whose value of resistor changes with the change in temperature. Thermistors are of two types. NTC and PTC.
NTC Thermistor | PTC Thermistor |
---|---|
Resistance decreases when temperature increases | Resistance increases when temperature increases |
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