In this article, Resistors and Applications of Resistors we will focus on the list below:

• • What is Resistor?

• • Mathematical Relations

• • Electronic Symbols

• • How to connect resistors in a circuit?

• • Application of resistors in a circuit

What is a resistor?

The resistor is an electronic component that limits the flow of current in the circuit.

The electrical resistance of a resistor is measured in ohms.

The symbol for an ohm is the Greek capital omega: Ω.

1000Ω = 1KΩ (1 killo Ω)

1000000Ω = 1MΩ (1 mega Ω)

Mathematical Relations of a Resistor

Resistances in series                  R = R1 + R2 + Rn

Resistances in parallel               1/R = 1/R1 + 1/R2 + 1/R3 + 1/Rn

Voltage drop                            V = IR where I is current,

Power dissipation                     P = I^2R = V2/R

Electronic Symbol of  Resistors

There are two symbols for the resistor, zigzag lines, and a rectangular box. Either of these two symbols is accepted to represent Resistor.

Variable Resistor

Symbol for Rheostat

The symbol for a voltage-dependent resistor (Varistor)

The symbol for negative temperature coefficient (NTC) resistor (thermistor)

The symbol for Heating Element resistor

Symbols for Light Dependent Resistor (LDR)

How resistors are connected in a circuit?

Resistors connected in series

Resistors connected in parallel

Applications of resistors in a circuit

Application of  Resistor as a Current Limiter:

Placement of the correct value of a resistor in series with Transistors, LEDs and other semiconductor components in a circuit limit the amount of current to what they need to function without being damaged.

Application of  Resistor as a Voltage Divider:

Resistors are connected together, one after the other, to form a series circuit, and voltage ratios will be obtained across each of them.

If the resistors are the same value, the voltage drop across each will be equal, otherwise, it would be proportional to the resistance of each resistor.

Voltage dividers are useful for components that need to operate at a lesser voltage than that supplied.

Application of  Resistor as a Timer and Frequency generator:

A good timing source can be obtained by connecting the resistor to a capacitor.

Such a combination can be found in

1. 1. Light flashers

1. 1. Electronic sirens

1. 1. And many other circuits depend on this feature to generate a pulse.

Application of  Resistor  in Controlling Volume, Light intensity and Motor Speed:

Variable Resistors allow the setting of resistance by sliding a slider or turning a knob. And varying the resistance allows us to change the amount of current flowing in a circuit.

Variable resistors are used to control the loudness of an amplifier, the pitch of a musical tone, the speed of a motor and light intensity.

Resistors can also be used as:

• • Shunts in ammeters and voltage meters

• • Damping agents in oscillators

• • Feedback networks in amplifiers

• • Pull-up for input-output line

• • Pull-down for input-output line

Applications of Thermistors include:

1. 1. Measurement and control of temperatures

1. 1. Time delay

1. 1. Temperature compensation

1. 1. Liquid level indicators.

Applications of Varistor include:

1. 1. Voltage surge

1. 1. Protective circuits

1. 1. Generation of non-sinusoidal waveform

Connection of resistor in a circuit