As an engineering student or practising engineer, it's important to have a solid understanding of resistors and their role in electrical circuits. This article will give you a comprehensive overview of resistors, including what they are, important calculations and equations, and key applications.

What are Resistors?

A resistor is a passive electrical component that resists the flow of electrical current in a circuit. It's essentially a device that converts electrical energy into heat, which is then dissipated into the surrounding environment. The amount of resistance provided by a resistor is measured in ohms, represented by the symbol Ω.

Resistor Equations and Calculations

When working with resistors, there are several important equations and calculations that you need to be aware of. These are:
  1. Ohm's Law

V = Voltage (V)
I = Current (A)
R = Resistance (Ω)

  1. Power Equation

P = Power (W)

Worked Example & Calculation tools

For the given circuit, find the total voltage of the circuit as well as the total power absorbed by the system.

  1. First Step: Find the voltage of the system using the total resistance and given the current

For our system, we can sum the total resistance as (600+400) Ω as they are connected in series.
Using this new value, we can calculate the voltage:





  1. Second Step: Using voltage and current, we can find the total power of the system.






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Conclusion: For the given circuit, we found the voltage to be 200V. Using this value, we could determine the total power dissipated by the system, which was 40W.

Concept Summary

Ohm's law states that the current flowing through a resistor is proportional to the voltage across it. The power equation relates the power dissipation in a resistor to the current flowing through it and the voltage across it.
Ohm’s Law and Power

Applications of Resistors

Resistors are used in various applications, from basic electrical circuits to complex electronic systems. Some key applications include:
  1. Voltage division: Resistors can be used to divide voltage in a circuit, for example, in a voltage divider circuit.
  2. Current limiting: Resistors can limit the current flowing through a circuit, protecting other components from damage.
  3. Impedance matching: Resistors can be used to match the impedance of one part of a circuit to another, for example, in a radio circuit.
  4. Signal processing: Resistors can be used in analog circuits to shape or filter signals, for example, in a low-pass filter.

Types of Resistors

There are two main branches of resistors:

Linear Resistors

Fixed Resistors

Thick Film Resistor

Thin Film Resistor

Carbon Composition Resistor

Wire-Wound Resistor

Variable Resistors



Trimmer Resistor

Non-linear Resistors





Resistors are a fundamental component in electrical circuits, playing a critical role in power control and regulation. Understanding the basic equations and calculations associated with resistors, as well as their key applications, is essential for anyone working in electrical engineering or any other engineering discipline. Whether you're a university student or a practising engineer, this knowledge will be invaluable in your work and help you design and build more effective electrical circuits.
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