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Glossary
Electrical Theory & Applications for HVACR
reactance
the effects of capacitance and/or inductance on an alternaƟng current circuit, expressed in ohms;
symbol is X
recƟficaƟon
the process of converƟng AC to DC
relay
an electromechanical device that can be energized with a relaƟvely small current to operate a set of
contacts carrying a larger current
resistance
opposiƟon to current flow
rheostat
a variable resistor that can be adjusted to various levels
root mean square (rms)
the effecƟve value of an alternaƟng periodic current or voltage, calculated as the square root of the
average of the squares of all instantaneous values of the current (or voltage) throughout one cycle
rotor
the rotaƟng part of a motor or generator
run winding
the motor winding that carries current during normal operaƟon
S
safety ground
the conductor that connects the equipment frame or chassis to earth ground; usually a green or bare
wire
safety motor control
a device operated by pressure, temperature, or current that opens the circuit if safe condiƟons are
exceeded
scale
a measurement band on a test instrument
secondary voltage
the output voltage of a transformer; can be higher or lower than primary voltage
series circuit
a circuit with only one path for current flow