22 Electrical Power Systems Technology
The load of a flashlight is a small incandescent lamp. When electri-
cal energy from the source is forced to pass through the filament of the
lamp, the lamp produces a bright glow. Electrical energy is first changed
into heat energy and then into light energy. A certain amount of the work
is achieved by the lamp when this energy change takes place.
The energy transformation process of a flashlight is irreversible. It
starts at the battery when chemical energy is changed into electrical ener-
gy. Electrical energy is then changed into heat energy and eventually into
light energy by the load device. This flow of energy is in a single direction.
When light is eventually produced, it consumes a large portion of the elec-
trical energy coming from the source. When this energy is exhausted, the
system becomes inoperative. The battery cells of a flashlight require peri-
odic replacement in order to maintain a satisfactory operating condition.
Flashlights do not ordinarily employ a specific indicator as part of
the system. Operation is indicated when the lamp produces light. In a
strict sense, we could say that the load of this system also serves as an
indicator. In some electrical systems the indicator is an optional system
part.
ENERGY, WORK, AND POWER
An understanding of the terms “energy,” “work,” and “power” is
necessary in the study of electrical power systems. The first term, “en-
ergy,” means the capacity to do work. For example, the capacity to light a
light bulb, to heat a home, or to move something requires energy. Energy
exists in may forms, such as electrical, mechanical, chemical, and heat. If
energy exists because of the movement of some item, such as a ball roll-
ing down a hill, it is called kinetic energy. If energy exists because of the
position of something, such as a ball that is at the top of the hill but not yet
rolling, it is called potential energy. Energy is one of the most important
factors in our society.
A second important term is “work.” Work is the transferring or trans-
forming of energy. Work is done when a force is exerted to move some-
thing over a distance against opposition, such as when a chair is moved
from one side of a room to the other. An electrical motor used to drive a
machine performs work. Work is performed when motion is accomplished
against the action of a force that tends to oppose the motion. Work is also
done each time energy changes from one form into another.