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Electrical Theory & Applications for HVACR
Chapter 1: What Is Electricity?
Page 3
What Is Electricity?
1
Electricity is a form of energy. Electrical energy is the movement of electrons through a conductor.
Other forms of energy include heat, light, chemical (baƩery), atomic (power plant), and mechanical
(motor). Energy cannot be created or destroyed, but it can be converted from one form to another.
For example, heat is used to produce electricity, which can be used to produce light. Electrical
appliances are designed to convert electrical energy to another form of energy, thereby performing
useful work. Some devices produce heat and others produce moƟon or light.
ATOMS/ELECTRONS
All maƩer is made of atoms. Atoms are made up of parƟcles called protons, neutrons, and electrons.
Protons and neutrons are located at the center, or nucleus, of the atom. Electrons travel in orbits
around the nucleus. Protons have a posiƟve charge, electrons have a negaƟve charge, and neutrons
have no charge and therefore no effect on the electrical characterisƟcs of the maƩer. Electrical
energy is released when electrons move from one atom to another; electrons can be forced to pass
from one atom to another. Atoms try to maintain equal numbers between posiƟve (+) and negaƟve
(‐) charges (protons vs. electrons). An atom that loses an electron becomes posiƟvely charged (+) due
to the excess proton. An atom that gains an extra electron becomes negaƟvely charged (‐).
The Law of Electric Charges states that like charges repel and opposite charges aƩract. Excess
electrons are aƩracted to atoms lacking electrons. To perform useful work, a constant and steady
movement of electrons must be produced.
POTENTIAL DIFFERENCE
An imbalance of electrons is called a potenƟal difference. A potenƟal difference describes a situaƟon
where excess electrons have accumulated, and are waiƟng for an opportunity to reconnect with
atoms that lack electrons. Electrons travel from negaƟve (‐) to posiƟve (+) atoms.
There are a variety of methods used to create a potenƟal difference (electromoƟve force) between
two points: fricƟon (staƟc electricity), chemical (baƩery), thermoelectric (heat), photoelectric (light),
and magneƟc (generator or alternator).
The presence of a potenƟal difference is someƟmes called electromoƟve force (EMF), which is further
abbreviated to “E.”
VOLTS
The potenƟal difference (EMF) between two points can be very high or very low. The unit of
measurement used to indicate the strength of the EMF is the Volt.