BASIC ELECTRONICS - OD1633 - LESSON 1/TASK 1
them at the negative terminal. Because the electrons repel each other (like
electrical charges repel), the electrons push out through the circuit and
flow to the positive terminal (unlike electrical charges attract). Thus, we
can see that an electric current is, in fact, a flow of electrons from
negative to positive.
This is the reverse of the original idea of current flow. Before scientists
understood what electric current was, they assumed that the current flowed
from positive to negative. Their studies showed that this was wrong; they
learned that current is the electron movement from negative (concentration
of electrons) to positive (lack of electrons).
d. Conductors and Insulators.
Any material that will allow electric
current to flow through it is an electrical conductor.
Any material that
blocks electric current flow is an electrical insulator.
Conductors are
used in automotive equipment to carry electric current to the electrical
system components.
Insulators are necessary to keep the electric current
from taking a shorter route instead of going to the intended component. The
electrical properties of a substance depend mainly on the number of
electrons in the outermost orbits of its atoms which cannot, at any time,
contain more than eight electrons.
(1) Conductors. Whenever there are less than four electrons in the
outer orbits of the atoms of a substance, these electrons will tend to be
free.
This will cause the substance to permit free motion of electrons,
making it a conductor (see figure 3 on the following page).
Electrical energy is transferred through conductors by means of the movement
of free electrons migrating from atom to atom within the conductor.
Each
electron moves a short distance to the neighboring atom, where it replaces
one or more electrons by forcing them out or their orbits.
The replaced
electrons repeat this process in nearby atoms until the movement is
transmitted throughout the entire length of the conductor, creating a
current flow. Copper is an example of a good conductor because it has only
one free electron. This electron is not held very strongly in its orbit and
can get away from the nucleus very easily.
Silver is an even better
conductor of
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