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.

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 stationary coil.

Consider a rectangular single turn coil rotating in a uniform magnetic field with a constant angular velocity ω rad/sec in the anticlockwise direction as shown in Figure 4.1