____ 30.
In the hardwired relay control circuit shown, when the switch is closed, CR
coil is:
a.
b.
c.
d.
____ 31.
In the motor starter circuit shown, the main contacts M are:
a.
b.
c.
d.
____ 32.
de-energized, the red light is off, and the green light is on.
energized, and the red and green lights are both on.
energized, the red light is off, and the green light is on.
energized, the red light is on, and the green light is off.
part of the power circuit.
part of the control circuit.
designed to handle the full load current of the motor.
both a and c.
The Boolean expression for the logic circuit drawn is:
a.
b.
Y=A+B+C
Y = (A + B)C
c.
d.
Y=AB+C
Y = ABC
____ 33.
In conventional logic circuits, binary 1 represents:
a. the presence of a signal.
c. a high voltage level.
b. the occurrence of some event.
d. all of these.
____ 34.
Which of the following number systems has a base of 16?
a. Binary-coded decimal
c. Gray code
b. Octal
d. Hexadecimal
____ 35.
The central processing unit:
a. serves only to supply power to the backplane.
b. serves only to store the program in memory.
c. looks at the outputs, makes the decisions based on the program, and
sets the inputs.
d. looks at the inputs, makes the decisions based on the program,
and sets the outputs.
____ 36.
Which logic circuit represents the Boolean expression
a. (d)
b. (a)
____ 37.
The scan time is the time required:
c. (b)
d. (c)
a.
b.
c.
d.
____ 38.
In order to energize the starter coil:
a.
b.
c.
d.
____ 39.
to record the status of all output devices.
to record the status of all input devices.
for the information to pass from input to output.
to execute one cycle of the total program.
the pressure switch, or the temperature switch, or the manual
pushbutton must be closed.
the pressure switch, and the temperature switch, or the manual
pushbutton must be closed.
the pressure switch, and the temperature switch, and the manual
pushbutton must be closed.
all of the above.
The symbol shown is that for a:
a.
b.
light sensor.
pressure sensor.
c.
d.
heat sensor.
proximity sensor.
____ 40.
The decimal number 28 would be written in binary as:
a. 01011.
c. 10110.
b. 00111.
d. 11100.
____ 41.
The main advantage of using the Gray code is:
a. it can be easily converted to decimal numbers.
b.
c.
d.
____ 42.
The Boolean equation for the logic symbol is:
a.
b.
____ 43.
Y= A + B
Y= AB
c.
d.
Y= A • B
either b or c.
Block No. 4 of the PLC block diagram represents the:
a.
b.
____ 44.
large decimal numbers can be written using fewer digits.
only one digit changes as the number increases.
it uses the number 2 as its base.
CPU.
programming device.
c.
d.
input module.
memory.
A(n) _________ bit is used to detect errors that may occur while a word is
moved.
a. parity
c. negative
b. positive
d. overflow
____ 45.
If a PLC has a total scan time of 10 ms and has to monitor a signal that
_____ then the controller may not detect this change.
a. is constantly changing
c. changes state twice in 5 ms
b. is fast
d. changes state once in 20 ms
____ 46.
The basic rule for an OR gate is:
a. if one or more inputs are 1, the output is 1.
b. if one or more inputs are 1, output is 0.
c. if one or more inputs are 0, the output is 1.
d. both band c.
____ 47.
23.1. The diagram shown is a:
a.
b.
____ 48.
input module wiring.
ladder logic program.
c.
d.
output module wiring.
relay schematic.
The Output Energize instruction:
a. signals the PLC to energize or deenergize the output.
b. is also known as the OTE instruction.
c. looks and operates like a relay coil.
d. all of these.
____ 49.
The symbol
in a ladder logic diagram
represents a:
a. field input sensing device.
c.v virtual relay coil.
b.
____ 50.
set of normally closed contacts.
d.
seal-in contact.
Solenoid valves are available to control:
a. oil flow.
c. water flow.
b. air flow.
d. all of these