Motor Controls II Final Exam Question
and Answers
If two of the lines supplying power to a three-phase motor are reversed, the motor will
not reverse the direction of rotation. - correct answer-False
The Hall effect was discovered by Edwin H. Hall at Johns Hopkins University in 1979. -
correct answer-False
The Hall generator cannot be used in a manner similar to a limit switch. - correct
answer-False
Proximity detectors are designed to detect the presence or absence of some object. -
correct answer-True
Sensors targeting specific types of metal should be mounted as close to other metals as
possible. - correct answer-False
Photodetectors can be used to sense the presence or absence of almost any object. -
correct answer-True
When the cad cell is in the presence of light, its resistance is high. - correct answer-
False
A decrease in frequency produces a decrease in inductive reactance. - correct answer-
True
Variable frequency drives intended to control motors under 500 horsepower generally
use SCRs or GTOs. - correct answer-False
The number of internal relays and timers contained in a PLC is determined by the
physical size of the computer. - correct answer-False
Before a program can be developed for input into a programmable logic controller, it is
recommended, but not necessary, to assign which devices connect to the input and
output terminals. - correct answer-False
Most analog sensors can produce only very weak signals. - correct answer-True
Insulators are generally made from lightweight materials that have small atoms. -
correct answer-True
, The diode is often called a PN junction. - correct answer-True
The conventional current flow theory assumes that current flows from positive to
negative. - correct answer-True
Diodes cannot be connected to produce full-wave rectification. - correct answer-False
The zener diode makes a very effective voltage regulator for the load circuit. - correct
answer-True
If no current flows through the base of the transistor, the transistor acts like a closed
switch. - correct answer-False
The unijunction transistor (UJT) is a special transistor that has two bases and two
emitters. - correct answer-False
The pulse rate is determined by the amount of resistance and capacitance connected to
the emitter of the UJT. - correct answer-True
____ timers operate by restricting the flow of air through an orifice to a rubber bellows or
diaphragm. - correct answer-Pneumatic
Programmable controllers contain ____ electronic timers. - correct answer-internal
NEMA-rated motors are designed to operate at plus or minus ____ percent of their
rated voltage. - correct answer-10
The percentage of heat rise in the motor caused by the voltage unbalance is equal to
____ times the percent squared. - correct answer-two
Two factors determine the polarity of the voltage produced by the Hall generator: the
direction of current flow and the ____ of the ____ field. - correct answer-polarity;
magnetic
____ are designed to produce an output voltage that is proportional to the strength of a
magnetic field. - correct answer-Linear transducers
____ proximity detectors will sense ferrous metals better than nonferrous. - correct
answer-All-metal
Many ultrasonic sensors have an analog output of voltage or current, the value of which
is determined by the ____. - correct answer-distance to the object
Photo-operated devices fall into one of three categories: photovoltaic, photoemissive,
and ____. - correct answer-photoconductive
and Answers
If two of the lines supplying power to a three-phase motor are reversed, the motor will
not reverse the direction of rotation. - correct answer-False
The Hall effect was discovered by Edwin H. Hall at Johns Hopkins University in 1979. -
correct answer-False
The Hall generator cannot be used in a manner similar to a limit switch. - correct
answer-False
Proximity detectors are designed to detect the presence or absence of some object. -
correct answer-True
Sensors targeting specific types of metal should be mounted as close to other metals as
possible. - correct answer-False
Photodetectors can be used to sense the presence or absence of almost any object. -
correct answer-True
When the cad cell is in the presence of light, its resistance is high. - correct answer-
False
A decrease in frequency produces a decrease in inductive reactance. - correct answer-
True
Variable frequency drives intended to control motors under 500 horsepower generally
use SCRs or GTOs. - correct answer-False
The number of internal relays and timers contained in a PLC is determined by the
physical size of the computer. - correct answer-False
Before a program can be developed for input into a programmable logic controller, it is
recommended, but not necessary, to assign which devices connect to the input and
output terminals. - correct answer-False
Most analog sensors can produce only very weak signals. - correct answer-True
Insulators are generally made from lightweight materials that have small atoms. -
correct answer-True
, The diode is often called a PN junction. - correct answer-True
The conventional current flow theory assumes that current flows from positive to
negative. - correct answer-True
Diodes cannot be connected to produce full-wave rectification. - correct answer-False
The zener diode makes a very effective voltage regulator for the load circuit. - correct
answer-True
If no current flows through the base of the transistor, the transistor acts like a closed
switch. - correct answer-False
The unijunction transistor (UJT) is a special transistor that has two bases and two
emitters. - correct answer-False
The pulse rate is determined by the amount of resistance and capacitance connected to
the emitter of the UJT. - correct answer-True
____ timers operate by restricting the flow of air through an orifice to a rubber bellows or
diaphragm. - correct answer-Pneumatic
Programmable controllers contain ____ electronic timers. - correct answer-internal
NEMA-rated motors are designed to operate at plus or minus ____ percent of their
rated voltage. - correct answer-10
The percentage of heat rise in the motor caused by the voltage unbalance is equal to
____ times the percent squared. - correct answer-two
Two factors determine the polarity of the voltage produced by the Hall generator: the
direction of current flow and the ____ of the ____ field. - correct answer-polarity;
magnetic
____ are designed to produce an output voltage that is proportional to the strength of a
magnetic field. - correct answer-Linear transducers
____ proximity detectors will sense ferrous metals better than nonferrous. - correct
answer-All-metal
Many ultrasonic sensors have an analog output of voltage or current, the value of which
is determined by the ____. - correct answer-distance to the object
Photo-operated devices fall into one of three categories: photovoltaic, photoemissive,
and ____. - correct answer-photoconductive
