Briggs & Stratton 86262GS Familiarization & Troubleshooting Manual page 7

Portable Generator Familiarization & Troubleshooting Guide
Section 1 • Generator Fundamentals
Several basic methods may be used to create an electrical
current flow. Four methods will be discussed here. All of
these methods are based on a fundamental law that energy
can never be created or destroyed but can be changed into
other forms of energy.Thus, chemical, heat, light and
magnetic energy can be changed into electrical energy.
The four basic methods of creating electrical current flow
are:
• Chemical energy (e.g., storage battery)
• Heat energy (e.g., thermocouple)
• Light energy (e.g., photo-electric)
• Magnetic energy (e.g., alternator or generator)
The Thermocouple
When two dissimilar metals are welded together and the
welded junction is heated or cooled, an electro-motive force
(EMF) is produced.The joining process appears to disturb
the atomic orbits at the junction, so that the outer electrons
in both metals are loosely held. Any small addition or
subtraction of heat energy will set these electrons free.
Figure 1.5 shows a union between iron and copper wires,
this union forms a thermocouple. In Figure 1.5A, the heat of
the flame has caused the copper atoms to lose electrons.
The copper draws electrons from the iron and a current
flow in one direction is produced.
In Figure 1.5B, the wire junction has been cooled, causing the
iron atoms to lose electrons and attract electrons from the
copper.The resulting current flow is then reversed from that
of Figure 1.5A.
CREATING CURRENT FLOW
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Figure 1.5 — The Thermocouple
Photoelectric Cell
Copper oxide and selenium oxide are sensitive to rays of
light. Materials that create a current flow when exposed to
light are said to be "photo-voltaic."
Magnetic Energy
Magnetism is closely related to electricity. It can be used to
produce electricity and electricity can be used to produce
magnetism. A study of one must, therefore, include a study of
the other.