Alternating Current

Relevance

Alternating current (AC) is a type of electric current in which the flow of electrons periodically reverses direction, following a si-nusoidal waveform. It is the standard form of electrical power in residential and industrial settings due to its efficient transfor-mation and long-distance transmission. Understanding AC is essential for analyzing the behavior of electrical components—such as resistors, capacitors, and inductors—in time-varying conditions. Moreover, AC principles are foundational in modern smart home systems, where the control and optimization of lighting, HVAC, and appliances rely on precise management of alternating signals and power flows within interconnected devices.

Abstract

This module provides a comprehensive introduction to the principles and applications of alternating current (AC), a fundamental topic in electrical engineering. Starting from the definition of AC as a time-varying electric current that reverses direction periodi-cally, the module explores the mathematical representation of sinusoidal waveforms, including amplitude, angular frequency, phase, and period. Students learn how to apply key relationships between frequency, period, and angular frequency, and gain experience through solved examples involving practical components and measuring instruments.

The module examines the behavior of ideal components—resistors, capacitors, and inductors—under AC excitation, focusing on voltage-current phase relationships and power dissipation. It introduces concepts such as instantaneous power, average (active) power, and reactive power, and explains the significance of root mean square (RMS) values in AC analysis. A dedicated section covers the use of phasors and complex numbers to simplify the solution of AC circuits, preparing students for more advanced circuit analysis.

Finally, the content highlights the importance of AC in real-world systems, including electric motors, power grids, and smart home technologies. By mastering these foundational concepts, students will be equipped to understand and design efficient, safe, and intelligent electrical systems based on alternating current.