AC (Alternating Current) Lecture Notes

Jul 24, 2024

AC (Alternating Current) Lecture Notes

Introduction

  • Alternating Current (AC) topic introduction.
  • The significance of understanding AC as per the updated syllabus.

Key Concepts of AC

Definition of Alternating Current

  • Changes its direction periodically.
  • Contrasts with Direct Current (DC).

Basic Equations

  • Voltage as a function of time: V = V_max * sin(ωt + φ) where V_max is the maximum voltage.
  • Current is represented by I = I_max * sin(ωt).

Key Definitions

  • Maximum Value (Peak Value): Highest point of AC, denoted as I_max.
  • Time Period (T): Time taken for one complete cycle of AC.
  • Frequency (f): Number of complete cycles per second, commonly 50Hz in many regions.

Average and RMS Values

Average Current

  • Defined as the constant current that sends the same amount of charge over a time period.
  • Average value calculated as area under the curve divided by the time period.
  • It represents 63% of the peak value in AC.

RMS (Root Mean Square) Value

  • RMS is defined as the square root of the average of the squares of instantaneous values.
  • RMS value for AC is I_rms = I_max / √2.

Circuits and Reactance

Types of Loads

  1. Resistive Load: Voltage and current are in phase.
  2. Inductive Load: Current lags voltage.
  3. Capacitive Load: Current leads voltage.

Formulas Related to Reactance

  • Inductive Reactance (X_L): X_L = ωL
  • Capacitive Reactance (X_C): X_C = 1/(ωC)

Impedance (Z) in AC Circuits

  • Z = √(R² + (X_L - X_C)²)
  • Represents the total opposition to the flow of AC current.

Series LRC Circuit Theory

  • Resonance Frequency (f_r): f_r = 1/(2π√(LC))
  • At resonance, inductive and capacitive reactances are equal.
  • Voltage and current relationships in inductive and capacitive components are key.

Generators and Maximum EMF

  • Maximum Electromotive Force (EMF) represented as E_max = E_0 sin(ωt).
  • Factors influencing the EMF in generators.

Example Problems

  1. Resonant Frequency Calculation: Calculate the resonant frequency given values of L and C.
  2. Peak Values: Understanding RMS and peak values through examples.

Conclusion and Homework

  • Recap of all discussed topics and important equations.
  • Homework assigned; engage in further practice problems.
  • Reminder to maintain a fun and engaging learning environment.
  • Instructor: Your Sh Ma'am, emphasizing that there is no fear in learning.
  • Encouragement: Stay engaged, and comment your homework responses!

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