VOLTAGE PRODUCED BY MAGNET-
Methods of Producing Electrical Power
ISM.--Magnets or magnetic devices are used for
thousands of different jobs. One of the most
The following is a list of the six most common
useful and widely employed applications of
methods of producing emf. Some of these
magnets is in the production of vast quantities of
methods are much more widely used than others.
electric power from mechanical sources. The
We will first define the methods for you, and then
mechanical power may be provided by a number
we will discuss them in more detail.
of different sources, such as gasoline or diesel
engines and water or steam turbines. However,
1. MAGNETISM--Voltage produced in a
the final conversion of these source energies to
conductor when the conductor moves through a
magnetic field, or when a magnetic field moves
principle of electromagnetic induction. We will
through the conductor in such a manner as to cut
discuss here the fundamental operating principle
the magnetic lines of force of the field.
2. FRICTION--Voltage produced by rubbing
To begin with, three fundamental conditions
two materials together.
must exist before a voltage can be produced by
3. PRESSURE (piezoelectricity)--Voltage
magnetism. These conditions are
produced by squeezing crystals of certain
1. a CONDUCTOR, in which the voltage will
4. HEAT (thermoelectricity)--Voltage pro-
duced by heating the joint (junction) where two
2. a MAGNETIC FIELD in the conductor's
unlike metals are joined.
5. LIGHT (photoelectricity)--Voltage pro-
3. a RELATIVE MOTION between the field
duced by light striking photosensitive (light
and the conductor. The conductor must be moved
so as to cut across the magnetic lines of force, or
the field must be moved so that the lines of force
6. CHEMICAL ACTION--Voltage pro-
are cut by the conductor.
duced by chemical reaction in a battery cell.
Figure 4-3.--Voltage produced by magnetism.