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S-1 General Safety Rules S-2 Effects of Electric Current S-3 On The Job S-4 Protective Clothing S-5 Ladders & Scaffolds S-6 Fires S-7 Ground Fault Circuit Interrupters S-8 Grounding
Unit 1 – Atomic Structure
Objectives After studying this unit, you should be able to: List the principal parts of an atom State the law of charges Discuss the centripetal force  Discuses the differences between conductors & insulators Preview Electricity is the driving force that provides most of the power for the industrialized world. It is used to light houses, cook meals, heat and cool building, run electric motors, & supplies ignition for most automobiles in the world, 
Electrical Theory Fundamentals
About Lesson

Welcome to our lesson on electrical resistors and their role in circuits. Resistors are fundamental components in electrical and electronic systems that control the flow of current. In this lesson, we will explore the characteristics of resistors, their various types, and how they are used in circuits. Let’s dive in!

I. Understanding Resistance: A. Definition of Resistance:

  • Resistance is the opposition to the flow of electric current in a circuit.
  • It is measured in ohms (Ω) and denoted by the symbol “R.”

B. Factors Affecting Resistance:

  1. Material:

    • Different materials have different resistivity values.
    • Common resistor materials include carbon composition, metal film, and wire-wound resistors.
  2. Length and Cross-Sectional Area:

    • Longer resistors have higher resistance, while shorter resistors have lower resistance.
    • Larger cross-sectional area leads to lower resistance, while smaller cross-sectional area increases resistance.
  3. Temperature:

    • Resistance generally increases with an increase in temperature for most materials.

II. Types of Resistors: A. Fixed Resistors:

  1. Carbon Composition Resistors:

    • Made from a mixture of carbon and a binder material.
    • They are inexpensive but less precise and have higher tolerances.
  2. Metal Film Resistors:

    • Made by depositing a thin film of metal alloy onto an insulating substrate.
    • They have better stability, accuracy, and lower tolerances compared to carbon composition resistors.
  3. Wire-Wound Resistors:

    • Made by winding a resistive wire around an insulating core.
    • They have higher power ratings and are used in high-power applications.

B. Variable Resistors:

  1. Potentiometers:

    • Also known as variable resistors or pot.
    • They have three terminals and can be adjusted to provide variable resistance.
  2. Rheostats:

    • Similar to potentiometers but with only two terminals.
    • They are used to control current by adjusting the resistance in a circuit.

III. Applications of Resistors: A. Current Limiting:

  • Resistors are commonly used to limit current flow in circuits and protect components from excessive currents.

B. Voltage Division:

  • In voltage dividers, resistors are used to create different voltage levels by dividing the total voltage across a circuit.

C. Signal Conditioning:

  • Resistors are used in various signal conditioning circuits, such as filters, amplifiers, and sensors.

D. Timing and Oscillators:

  • Resistors are critical in timing circuits, oscillators, and pulse generation circuits.

IV. Resistor Color Code: A. Overview:

  • To identify the resistance value of a resistor, a color code system is used.
  • The code consists of colored bands that represent numerical values.

B. Band Colors and Values:

  • Black (0), Brown (1), Red (2), Orange (3), Yellow (4), Green (5), Blue (6), Violet (7), Gray (8), White (9).
  • Gold and silver bands represent tolerance values.

Conclusion: In conclusion, resistors are essential components in electrical circuits, providing control over current flow and performing various functions like current limiting, voltage division, and signal conditioning. By understanding the properties of resistors, their types, and applications, you can effectively design and analyze circuits. Keep exploring the fascinating world of electronics, and remember to apply your knowledge to real-world projects.

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