Lesson 1/Learning Event 2
Learning Event 2:
DESCRIBE FUNDAMENTALS OF ELECTRICAL CIRCUITS AND SYMBOLS
Atoms from different elements are not alike. Electrical current will flow through some materials
easily but, in others, practically no electrons will flow. If current flows through a material easily,
the material is called a CONDUCTOR.
A good conductor is a material that has a large number of free electrons. All metals are conductors
of electricity, but some are better conductors than others. Examples of good conductors are silver,
copper, and aluminum. Silver is a better conductor than copper, but copper is more widely used
because it is cheaper. Since aluminum is light, it is used as a conductor where weight is a major
The ability of a material to conduct electricity also depends on its size. The greater its diameter
and the shorter its length, the better it conducts. Conductors may be in the forms of bars, tubes,
or sheets, but the most common form is wire. Many sizes of wire are used, from the fine hair-like
wire in sensitive measuring instruments to the large bar-like wire used for carrying high current in
power generating plants.
Most wire conductors that you will be working with on automotive vehicles are stranded wires. A
stranded wire consists of many small wires twisted together to make one conductor. This makes
them very flexible so they can be bent and fitted around vehicle components without breaking.
If a material has so few free electrons that it blocks electron flow, it is called an INSULATOR.
No material known is a perfect insulator, but some materials are such poor conductors that for all
practical purposes they are classed as insulators. Examples of insulators are porcelain, glass, air,
rubber, oil, Bakelite, and certain kinds of enamel and varnish.
Insulators are used to make sure that the flow of electrons does not stray out of the path that has
been provided with conductors. An example of this is the insulator used to anchor overhead
electric lines to their utility poles. The insulators block the electrons to prevent them from flowing
into the pole and into the ground.