What is a resistor?

 



 

Resistors are passive electrical components that limit electric current.

Resistor is a passive electrical component. Its primary function is to limit the flow of electric current.



To understand the function and working of resistors, let us consider an uniform hollow pipe with water flowing through it. If the two similar pipes are now joined with a narrow pipe relatedly having less diameter or cross-sectional area. Then the water current will be resisted by the pipe having less cross-sectional area. It means this particular section of pipe will act as a resistor for water current. Similarly, a resistor by limiting or reducing the flow of charge carrier, reduces the flow of electric current in a circuit.





What is OHM’S Law?

Voltage across a resistor is directly proportional to the current passing through it.




Vµ I

or, V=R.I


Where, R is a proportionality constant, it is called resistance of a resistor.  

It means that if the current through a resistance is required to increase, the value of potential difference or applied voltage across the resistor is required to increase.



Example: To use a LED (Imax =1 mA, RLED » 0Ω), without damage, in series with a voltage source of 9 Volt, find out the minimum resistance value of a resistor required to connect in series with the power supply.

Solution :

As per Ohm’s Law V=R.I

For Imax =1 mA, current ‘I’ should be less than or equals to 1 mA, i.e.

I ≤ 1 mA

V= 9 V

Rmin ≥ V/I,

Rmin ≥  9Volt/1mA ≥ 9 . 103 Ω ≥ 9kΩ


Types of Resistors:

1.   Linear Resistors

a)  Fixed Resistors

i.             Carbon Composition Resistors

ii.            Wire Wound Resistors

iii.           Thin Film Resistors

A.  Carbon Film

B.   Metal Film

iv.          Thick Film Resistors

A.  Fusible Resistors

B.   Metal Oxide Resistor

C.  Cermet Resistors        

b)  Variable Resistors

i.             Potentiometer

ii.            Rheostats

iii.           Trimmer

2.   Non-Linear Resistors

a)  Photo Resistors or Light Dependent Resistors

b)  Thermistors

c)  Varistors

d)  SMD Resistors






1.     Linear Resistors: Linear Resistors are those resistors, which current values changes with the change in applied voltage. In other words, we can say that a resistor, which current value is directly proportional to the applied voltage is known as linear resistors. Linear resistors are Ohmic devices and follows the Ohm’s law.

 

2.     Non-Linear Resistors: Non-Linear Resistors are those resistors, which current values does not change with the Ohm’s Law. In case of Non-Linear Resistors, the current value changes with change in applied temperature, light intensity falling on it. Non-Linear resistors are Non-Ohmic devices and do not follow the Ohm’s law.









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