http://www.ck12.org Chapter 19. Electromagnetism
FIGURE 19.8
A generator converts mechanical energy
into electrical energy, whereas a motor
converts electrical energy into mechanical
energy.you a demonstration of this phenomenon in class where a hand crank is attached to the motor spindle to allow for
easier (and more rapid) turning.
A generator is a device which converts mechanical energy into electrical energy. In very simple terms, turning a coil
in a magnetic field is the basis for an electric generator. It is also the way most of the electrical energy is generated
around the world. The voltage provided by the electrical outlets (such as the ones found in your home) is an induced
voltage, created by a generator of some sort. One of the greatest challenges nowadays is in finding cheap, renewable,
and clean energy sources with which to power the generators.
An example of “clean” energy is hydroelectric power. Falling water from dams is used to turn turbine generators,
Figure19.9. Wind is sometimes used to turn turbines as well. But most generators are driven by steam. Steam is
produced by heating water. The energy used to heat the water is primarily from nonrenewable, polluting, fossil fuels
and nuclear energy.
FIGURE 19.9
A typical turbine generator.Generators Produce Alternating Current
Notice that as the loop turns toward the north pole of the magnet inFigure19.8, the flux is reduced through the
loop. This is analogous to moving the north pole of a magnet away from a stationary loop. As the flux decreases, the
induced current produces magnetic field lines in the same direction as the permanent magnet in the figure obeying
Lenz’s law. However, after the loop has passed the point where there is zero flux through it (red sides parallel to the