A Resistor acts as a main electronic component in regulating or limiting the flow of an electric current in an electrical circuit. It is mainly used in electronic circuits because it acts as a current controller, it controls high and low voltage and it protects the components. The resistor mainly helps in regulating the flow of electricity in a circuit and it achieves the desired circuit behavior. Resistors are mainly used in electronic networks and electrical circuits to prevent the excess flow of current and to set the voltage levels in the circuit.

What is a Resistor?

The resistor can be defined as a passive electronic component with two terminals that produce electrical resistance to the flow of current in a circuit. It is measured in ohm(Ω). The Dimensional formula for a resistor is given as [Tex]ML^2A^{-2}T^{(-3)}[/Tex]. It can control limit or divide the electric current provided in the circuit, and its value can be determined by its resistance rating.

A Resistor contains four bands as shown in the below image:

• Band A in a resistor represents 1st digit.
• Band B in a resistor represents the 2nd digit.
• Band C in a resistor represents a Multiplexer.
• Band D in a resistor represents the % of Tolerance.

Symbol of Resistor

The Symbol Resistor can be represented as :

Symbol of Resistor

The Resistor can be denoted by its Value and name like R1 , R2 .The terminals of the resistor are represented by each lines which are extending from the squiggle or rectangle. The resistance value, typically expressed in ohms, is fundamental for circuit analysis and construction.

Different Types of Resistors

There are different types of resistors, which are mainly classified into

• Linear Resistors
• Non-Linear Resistors.

Types of Resistor

Linear Resistors

In Linear Resistors, the value of resistance changes based on the applied temperature and voltage. These Linear Resistors are again classified into Fixed and Variable Resistors.

1. Fixed Resistors: In Fixed Resistors, the value of resistance is fixed and cannot be changed. These are mostly used in fixed circuits because the resistance value is fixed. Fixed Resistors are mainly used in electronic circuits where a stable or fixed resistance is required, For example: in voltage dividers or current limiters. Fixed Resistor follows Ohm’s law, which states, that voltage (V) is directly proportional to current (I) and resistance (R).

There are different types of Fixed Resistors:

• Carbon Film Resistor
• Wire Wound Resistor
• Metal Film Resistor

2. Variable Resistors: In Variable Resistors, the value is not specific and can be changed and can manually adjust the value of resistance by using the dial, knob of a screw. It is also known as potentiometer having two connecting wires instead of three. Variable Resistors are mainly used in applications where resistance needs to be variable, for example: in volume controls or sensor applications or radio receiver. There are the different types of Variable Resistors:

• Potentiometer
• Rheostat Resistor
• Trimmer Resistor

Non-Linear Resistors

In non-linear resistors, the value of resistance changes significantly with changes in voltage or current in an electrical circuit. This indicates the relationship between voltage and current is not proportional and it do not follow Ohm’s law. The resistor values change according to the temperature and voltage applied in the circuit. Non-linear resistors are mainly used in applications where resistance needs to be change based on the applied voltage or current. Non-linear resistors are mainly used in applications like voltage regulation or precise control.

There are different types of Non-Linear Resistors:

• Thermistors
• NTC (Negative Temperature Coefficient) Thermistor
• PTC (Positive Temperature Coefficient) Thermistor
• Varistors
• Photo Resistors

Resistor Color Code

The value of resistance offered by a resistor is marked using a color code called Resistor Color Code. The resistors we use are very tiny and the printing of the value of resistance in the resistor is not feasible. Thus, to find the value of the resistor we use various color bands(mainly four color bands) that help to determine the value of the resistance. These color bands on the resistor are called the Resistor Color Codes.

1. Mnemonic of Resistor Color Code: Learning the Resistor Color Coding is very important and the mnemonic used to find the value of the resistor is:

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• The capital letters represent the first letters of the colors and their positions in the digit values. The representation of the color code as,
• Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, and White

Combination of Resistors

Resistors are used in various combinations. There are two methods of arranging the resistors in different combinations:

• Resistors in Series Combination
• Resistors in Parallel Combination

Equivalent Resistance: The equivalent resistance of combinations of resistors in series is equal to the sum of their individual resistances in the circuit.

1. Resistors in Series Combination

Two or more resistances are said to be connected in series when they are connected end to end and the same current flows through each of them in turn. In this case, the equivalent or the total resistance equals the sum of the number of individual resistances present in the series combination.

Mathematically, the equivalent resistance of any number of resistances (R1, R2, R3, R4, R5, ……..) connected in series is given as:

Req = R1 + R2 + R3 + R4 + R5 + ……..

2. Resistors in Parallel Combination

Two or more resistances are said to be connected in parallel connected when they are connected between two points and each has a different current direction. The current is branched out and recombined as the branches intersect at a common point in such circuits.

Mathematically, the equivalent resistance of any number of resistances (R1, R2, R3, R4, R5, ……..) connected in parallel is given as:

1/Req = 1/R1 + 1/R2 + 1/R3 + 1/R4 + 1/R5 + …..

Power Dissipated in a Resistor

The Formula for the power Dissipation in the resistor can be given as

[Tex]P=I^2R=VI=V^2[/Tex]

The following equation is derived from Joule’s law and Ohm’s law.

Working Principle of Resistor

Resistor is an passive electronic component which limits the flow of electric current in an electric circuit. It works on the principle of electrical resistance. It works mainly on resistance of an electrical circuit. Resistance has a property to opposes the flow of electric current. Resistance is measured in ohms(Ω).The more and the higher the resistance value of a resistor, the more it can restricts the flow of current passing through it.

By using Ohm’s Law: Resistor working principle can be explained using Ohm’s Law, which states that the current (I) flowing through a conductor is directly proportional to the voltage (V) across it and it is inversely proportional to its resistance (R). Mathematically, Ohm’s Law is represented as follows : V = I * R

Where,

• V stands for, the voltage across the resistor in volts (V).
• I stands for, the current passing through the resistor in amperes(A).
• R stands for, the resistance of the resistor in ohms(Ω).

Calculate the Resistance Value

• We need to consider the specific requirements of your circuit.
• We need to use Ohm’s law (R = V/I) to calculate it based on the required voltage (V) and current (I).
• We need to use R=V/I is the formula to calculate resistance value.

Difference between Resistor and Resistance

Given below is the difference between resistor and resistance