Basic Electricity
Safety should always be the first concern
whenever the task involves electricity.
All State and Local Safety Codes should
be followed when performing any
procedures outlined in this or any of our
training modules.
NEVER ATTEMPT TO WORK ON ANY
ELECTRICAL EQUIPMENT WITHOUT
PROPER TRAINING.
Never test a system without first testing
for improper shorts or grounds.
All matter consists of atoms. All atoms
contain electrons.
There are two bands of electrons, an
inner and an outer band. The free
electrons travel in the outer band.
Any material containing atoms with
free electrons is considered a
conductor of electricity. The more free
electrons a material has, the better
conductor of electricity it is.
Any metal will conduct electricity.
Gold, aluminum, mercury and copper
are the most efficient conductors of
electricity.
Gold is very expensive. Aluminum is
inexpensive, but has a corrosive
nature. Mercury is difficult to contain.
Copper is relatively inexpensive and
only mildly corrosive.
Copper is the most commonly used
material to carry electricity. Copper is
also flexible which adds to it's appeal.
Insulation is material that does not
conduct electricity. Insulation is used to
contain the electricity while it is in route
to the device using the electricity.
Light bulbs, electric motors and
electromagnetic coils (used to operate
electric valves and automatic switches)
are examples of devices that use
electricity.
Copper wire wrapped with insulation
is commonly used to provide these
devices with electricity.
"Electricity" is the term used to
describe free electrons flowing from
one atom to another.
An electron will flow from one atom to
another when the conductor (such as
a copper wire) is passed through a
magnetic field. Either the wire or the
magnetic field must move to
mechanically produce electricity.
An electron can be forced to move
from one atom to another using
chemicals (a battery).
There are several types of batteries.
Wet cell and dry cell are the most
common.
Another method of producing
electricity is called "static electricity".
Rubbing synthetic materials (such
as latex and glass) can produce
static electricity.
Lightning is a natural method of
producing electricity. Benjamin Franklin
was the first to capture the electrical
current from a lightning storm using a
wire as a kite tether. He invented the
lightning rod.
Alessandro Volta, an Italian physicist,
invented the battery; thus the term
"Volt", meaning electrical potential.
The scientific law that governs
electricity is known as OHM's Law.
Several mathematical formulas are
used to determine the characteristics
of electrical efforts.
Terms used to describe the electrical
effort are important to understand.
Common terms and their definitions
are:
Voltage: potential difference,
electrical pressure (volts).
Symbol "E".
Amperage: current flow, intensity of
flow of current. Common term (amps).
Symbol "I".
Resistance: restricting the flow of
current, measured in (ohms).
Symbol "R".
Power: the amount of current used.
Measured in (Watts).
Symbol "P".
Ohm's Law is very helpful to
determine unknowns when
diagnosing electrical problems.
OHM's Law
Voltage divided by amps is equal
to resistance
(E/I=R)
Voltage divided by resistance is
equal to amps
(E/R=I)
Amperage multiplied by resistance
is equal to voltage
(I*R=E)
Voltage multiplied by amps is equal
to watts
(E*I=P)
Example:
If 12 volts is applied to 12 ohms of
resistance, 1 amp of current will flow.
The amount of power used will be
12 watts.
Note: these formulas work for
"resistive" circuits only. Other, more
complicated formulas, are available
through Ohm's law for "inductive
reactive" circuits.
Inductive reactive circuits use
magnetic fields to perform work. The
resistance to the flow of current
changes from their static values after
current begins to flow.
Reactive circuits will be covered
in a later module.
A simple electrical circuit consists of
a source of power, a conductor,
a switch, and a load.
A flashlight is a good example of a
simple electrical circuit.
A flashlight has a battery (source),
wires connected to the battery
(conductor), the (switch) activated by
the thumb of the hand holding the
flashlight, and the bulb in the head
of the flashlight is the (load).
A load, in order to perform it's task,
must have the proper voltage applied.
The voltage is carried to the load with
the conductor and the switch controls
the flow of the current to the load.
When the switch is "open" no light
will shine. With the switch "closed"
the light will shine.
If the light bulb is burned out the
resistance to the current flow will be
so great (increasing), it will prevent the
flow of current. When the voltage
remains the same and the resistance
increases, the watts (amount of light)
decreases.
In this case, no current will flow, which
causes no light to shine.
This concludes the Basic Electricity Module
Stay in contact for more
Electrical Modules