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Chapter 1: What Is Electricity?
Electrical Theory & Applications for HVACR
only. In an AC circuit (alternaƟng current), the electrons are constantly changing direcƟons. In the
United States, power is transmiƩed at 60 hertz. This means the change from negaƟve to posiƟve
occurs 60 Ɵmes per second.
Electricity is oŌen compared to the flow of water. However, water valves and electrical switches
operate differently. Water flows when a valve is opened. Electricity flows when a switch is closed;
electrons cannot flow through an open switch or a broken wire. Any opening in the circuit (pathway)
is much like a drawbridge.
Switches are used in electrical circuits to act as these “drawbridges” for stopping and starƟng the flow
of electrons.
AMPERAGE
The words
ampere, amperage, amps
, and
current
are frequently used to describe the quanƟty and
intensity of electrons moving through a conductor. Amperage determines how much electricity will
be converted to another form of energy. Thus, electrical loads are “energy conversion devices.”
These energy conversion devices (toasters, light bulbs, motors, etc.) are used to perform useful work.
An ammeter is used to measure the quanƟty and intensity of electrons flowing inside a wire, or
through a load. The leƩer “I” (for “intensity”) is oŌen used to indicate amperage flow. When current
flows through a conductor, a magneƟc field is created. The clamp‐on ammeter is most commonly
used on AC circuits and is designed to read the intensity of flow in ONE wire. The magneƟc fields will
cancel each other out and the ammeter will indicate a reading of zero when clamped around the two
wires feeding a load device. If the same wire is coiled through the jaws of the ammeter, the reading
will increase by the mulƟple of each wrap of the coil. With an amperage reading of 20, and the wire
coiled 5 Ɵmes, the actual amperage for the circuit will be 4. Figure 1‐4 illustrates a typical clamp‐on
ammeter. These are available in analog type (needle pointer) or digital readout.
Fig. 1‐3: The negaƟve atom has 4 electrons and the posiƟve atom has 2
electrons.