Automotive Electrical and Electronic Systems Classroom Manual Fifth Edition Update by John F. Kershaw

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Introduction to Electricity 31
SUMMARY
The Greeks discovered the first type of electricity
in the form of static electricity when they observed
that amber rubbed with fur would attract lightweight
objects such as feathers. Static electricity is
electricity at rest or without any motion. All matter
is composed of atoms and electrical charge is a
component of all atoms, so all matter is electrical
in essence. An atom is the smallest part of an element
that retains all of the properties of that element.
All atoms share the same basic structure. At
the center of the atom is the nucleus, containing
protons, neutrons, and electrons. When an atom is
balanced, the number of protons will match the
number of electrons and the atom can be described
as being in an electrically neutral state. The phenomenon
we describe as electricity concerns the
behavior of atoms that have become, for whatever
reason, unbalanced or ionized. Electricity may be
defined as the movement of free electrons from one
atom to another.
An electrostatic charge can build up on the surface
of your body. If you touch something, your
charge can be discharged to the other surface,
which is called electrostatic discharge (ESD). An
automotive technician should always use a static
grounding strap when working with staticsensitive
electronic devices.
When light contacts certain materials, such as
selenium and cesium, electron flow is stimulated
and is called photoelectricity. Solar energy is light
energy (photons) from the sun that is gathered in a
photovoltaic solar cell. A photon is pure energy
that contains no mass. Thermoelectricity is electricity
produced when two dissimilar metals are
heated to generate an electrical voltage. A thermocouple
is a small device made of two dissimilar
metals that gives off a low voltage when heated.
Piezoelectricity is electricity produced when materials
such as quartz or barium titanate are placed
under pressure. The production of electricity from
chemical energy is demonstrated in the lead-acid
battery. Electromagnetic induction is the production
of electricity when a current is carried through
a conductor and a magnetic field is produced.
Andre Marie Ampere established the importance
of the relationship between electricity and
magnetism. Alessandro Volta discovered that if
two dissimilar metals were brought in contact
with a salt solution, a current would be produced;
this invention is now known as the battery.
George Simon Ohm showed a relationship
between resistance, current, and voltage in an
electrical circuit; he developed what is known as
Ohm’s Law. James Watt developed a method
used to express a unit of electrical power known
as Watt’s Law.