# Sinusoidal AC Voltage Generation

### How AC Voltage is generated?

Sinusoidal ac voltages are available from a variety of sources. The most common source is the typical home outlet, which provides an ac voltage that originates at a power plant; such a power plant is most commonly fueled by water power, oil, gas, or nuclear fusion. In each case an ac generator (also called an alternator), as shown in Fig. 1(a), is the primary component in the energy-conversion process.
Fig. 1: Various sources of ac power: (a) generating plant; (b) portable ac generator; (c) wind-power station; (d) solar panel; (e) function generator
The power to the shaft developed by one of the energy sources listed will turn a rotor (constructed of alternating magnetic poles) inside a set of windings housed in the stator (the stationary part of the dynamo) and will induce a voltage across the windings of the stator, as defined by Faraday's law, $$e = N {d\Phi \over dt}$$ Through proper design of the generator, a sinusoidal ac voltage is developed that can be transformed to higher levels for distribution through the power lines to the consumer. For isolated locations where power lines have not been installed, portable ac generators [Fig. 1(b)] are available that run on gasoline. As in the larger power plants, however, an ac generator is an integral part of the design.
In an effort to conserve our natural resources, wind power and solar energy are receiving increasing interest from various districts of the world that have such energy sources available in level and duration that make the conversion process viable. The turning propellers of the wind-power station [Fig. 1(c)] are connected directly to the shaft of an ac generator to provide the ac voltage described above. Through light energy absorbed in the form of photons, solar cells [Fig. 1(d)] can generate dc voltages. Through an electronic package called an inverter, the dc voltage can be converted to one of a sinusoidal nature. Boats, recreational vehicles (RVs), etc., make frequent use of the inversion process in isolated areas.
Sinusoidal ac voltages with characteristics that can be controlled by the user are available from function generators, such as the one in Fig. 1(e). By setting the various switches and controlling the position of the knobs on the face of the instrument, one can make available sinusoidal voltages of different peak values and different repetition rates.
The function generator plays an integral role in the investigation of the variety of theorems, methods of analysis, and topics to be introduced in the chapters that follow.