CHAPTER 4
ELECTRICAL THEORY
AND MECHANICAL THEORY
In this chapter we will discuss electrical theory
electricity, but tremendous strides have been made
and mechanical theory and how you will use these
in harnessing and using it. Elaborate theories
theories in the everyday performance of your
concerning the nature and behavior of electricity
assigned tasks. During our discussion we will
have been advanced and have gained wide
demonstrate a few examples of the theories that
acceptance because of their apparent truth and
are pertinent and/or necessary to you at your
demonstrated workability.
level of training. You need to understand the
basic laws and principles of electrical theory and
LAWS
mechanical theory to form a foundation for the
further development of your knowledge. It
By learning the rules and laws applying to the
is our intention to ensure you understand the
behavior of electricity and by understanding the
basics before you attempt the practical application
methods used to produce and control electricity,
of these theories. The practical application of
you may learn about electricity without ever
electrical theory and mechanical theory will be
having determined its fundamental identity. Your
discussed in later chapters. To fully grasp and
persistence and ability to sort out facts and ask
understand the laws and principles discussed in
detailed questions will determine how thoroughly
this chapter, you should be familiar with the
you understand electrical theory and laws,
knowledge provided in the NEETS training
and how they pertain to you. For an indepth
modules 1 through 5 and Basic Machines,
discussion of the basic laws of electricity, you
NAVEDTRA 10624-A.
should study NEETS, module 1.
After studying this chapter, you should be able
to (1) state the pertinent laws and principles of
electrical theory (Ohm's, Kirchhoff's, Coulomb's,
Ohm's Law
and the law of magnetism); (2) recognize the
requirements needed to produce and the various
In the early part of the nineteenth century,
methods used for electric power generation; (3)
George Simon Ohm proved by experiment that
state the basic laws and principles of mechanical
a precise relationship exists between current,
theory (Charles's, Boyle's, Pascal's, and Newton's
voltage, and resistance. This relationship is called
first, second, and third laws, and Bernoulli's
Ohm's law. It states that
principle); (4) describe energy and explain its
different forms; (5) relate the theory of leverage
the current in a circuit is DIRECTLY
to the moving and lifting of objects; (6) recognize
proportional to the applied voltage and
the different temperature scales and point
INVERSELY proportional to the circuit
out their relationship to each other; and
resistance.
(7) identify the different types of pressure (gauge,
atmospheric, barometric, and absolute) and point
Simply stated, this means that as the resistance
out their relationship to each other.
in a circuit increases, the current decreases
proportionally.
ELECTRICAL THEORY
Kirchhoff's Voltage Law
Electrical theory is just that, THEORY.
Presently, little more is known than the ancient
In 1847, G. R. Kirchhoff extended the use of
Greeks knew about the fundamental nature of
Ohm's law by developing a simple concept
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