Page 24 - Basics of Electrical, Electronic and Communication

Chapter 4

Single Phase AC Circuits

4.1 AC Fundamentals

An alternating voltage is any voltage that varies both in magnitude
and polarity with respect to time. Similarly an alternating current is
any current that varies both in magnitude and direction with respect to
time. An ac circuit is a circuit in which alternating current flows that
reverses its direction at regular intervals of time. Alternating current
systems have many advantages compared to direct current systems.
Alternating currents can be easily generated, transmitted and utilized
as compared to direct current systems.

4.2 Generation of sinusoidal emf

A sinusoidal voltage can be generated either by rotating a coil in a
stationary magnetic field or by rotating a magnetic field within a sta-
tionary coil.
Consider a rectangular single turn coil rotating in a uniform mag-
netic field with a constant angular velocity ω rad/sec in the anticlock-
wise direction as shown in Figure 4.1.

59