All handouts Flashcards
1
Q
When using in an industrial sensing application, a heated metal will A: contract B: expand C: melt D: none of the above
A
B: expand
2
Q
Two dissimilar metals bonded together have A: a high expansion rate B: a low expansion rate C: different expansion rate D: none of the above
A
C: different expansion rate
3
Q
If electrical contacts are permitted to open and close slowly A: poor contact pressure will result B: contacts burn-out can occur C: a and b D: neither a or b
A
C: a and b
4
Q
A metal that remains in a liquid stage at room temperature is A: Copper B: brass C: tin D: mercury
A
D: mercury
5
Q
A RTD is made of A: Copper wire B: platinum wire C: chrome wire D: iron wire
A
B: platinum wire
6
Q
A bellows type thermostat works on a change in A: heat principals B: movement principles C: resistance principles D: pressure principles
A
D: pressure principles
7
Q
A device that heats two dissimilar metals to produce a voltage is known as a A: thermostat B: thermometer C: thermoreactor D: thermocouple
A
D: thermocouple
8
Q
Two or more thermocouples connected in series are known as a A: thermopile B: thermostat C: a and b D: neither a or b
A
A: thermopile
9
Q
A device that works on the principles of a change in resistance with a change in heat is known as a A: resistance temperature detector B: thermocouple C: thermometer D: thermopile
A
A: resistance temperature detector
10
Q
Thermistors exhibit a \_\_\_\_\_\_\_\_\_\_ change of resistance at a certain temperature A: rapid B: linear C: gradual D: a and b
A
A: rapid
11
Q
A hall generator is constructed as a A: coiled device B: vacuum device C: capacitive device D: integrated device
A
D: integrated device
12
Q
Materials used to shunt a magnetic field away from objects is known as a A: detector B: reactor C: pulser D: reluctor
A
D: reluctor
13
Q
Proximity detectors are basically A: light detector B: heat detector C: metal detector D: all of the above
A
C: metal detectors
14
Q
Proximity detectors will more easily detect \_\_\_\_\_\_\_ because it is ferrous A: copper B: iron C: brass D: aluminum
A
B: iron
15
Q
A hall sensor is used to sense the presence of A: an electrical field B: heat C: a magnetic field D: none of the above
A
C: a magnetic field
16
Q
If a disk with magnetic poles around its circumference is attracted to a rotating shaft, and a hall sensor is mounted near the disk, the hall sensor A: will sense the poles as they pass by B: can be used to sense the present C: can be used as a tachometer D: all of the above
A
D: all of the above
17
Q
With proximity detectors, sensors should be mounted as
A: far away from each other as possible
B: close to each other as possible
C: close to ferrous materials as possible
D: all of the above
A
A: far away from each other as possible
18
Q
A proximity detector that detects non-metallic objects operate in a change in A: resistance B: capacitance C: inductance D: impedance
A
B: capacitance
19
Q
Most capacitive proximity detectors can sense the presence of A: wood B: copper C: brass D: all of the above
A
D: all of the above
20
Q
Most capacitive proximity detectors have a range of approximately A: 5mm B: 10mm C: 25mm D: 100mm
A
C: 25mm
21
Q
Ultrasonic detectors have a wide range of adjustable A: frequency B: sensing speed C: sensing distance D: physical size
A
C: sensing distance
22
Q
Ultrasonic detectors emit a A: low frequency sound B: high frequency sound C: low frequency radio wave D: high frequency radio wave
A
B: high frequency sound
23
Q
Photodetector detect A: sound B: mechanical motion C: light D: heat
A
C: light
24
Q
Compared to most other photodetector, a photoemissive device are a A: more reliable device B: slower device C: smaller in size D: faster device
A
D: faster device
25
```
When exposed to light, a photoconductive device change
A: voltage
B: resistance
C: the direction of current flow
D: the polarity of voltage applied
```
B: resistance
26
```
Photo detectors with both transmitter and receiver mounted in one housing need
A: refractor to operate
B: LED to operate
C: a cad cell to operate
D: reflector to operate
```
D: reflector to operate
27
```
Photo detectors can be used to sense the presence or absence of
A: almost any object
B: light absorbing object
C: objects with holes in them
D: none of the above
```
A: almost any object
28
```
Sensors and detectors can be used in a manner similar to a
A: limit switch
B: pressure switch
C: float switch
D: any digital device
```
D: any digital device
29
```
Squirrel cage induction motos are characterized by
A: simplicity
B: ruggedness
C: reliability
D: all of the above
```
D: all of the above
30
```
An excellent choice for alternating current, all purpose, constant speed motor applications would be a
A: dc motor
B: squirrel cage motor
C: stepping motor
D: none of the above
```
B: squirrel cage motor
31
```
The part of a squirrel cage motor that remains stationary is called the
A: shaft
B: armature
C: rotor
D: stator
```
D: stator
32
```
The part of the squirrel cage motor that rotates is called the
A: armature
B: rotor
C: stator
D: none of the above
```
B: rotor
33
```
The stator for a squirrel cage motor never has fewer than
A: 2 poles
B: 4 poles
C: 6 poles
D: 8 poles
```
A: 2 poles
34
```
A squirrel cage motor with one pare of poles, powered by a 50hz ax source will run at
A: 50r/min
B: 60r/min
C: 3000r/min
D: 3600r/min
```
C: 3000 r/min
35
```
A squirrel cage motor with 6 poles, powered by a 60hz ac source will run at
A: 600r/min
B: 1200r/min
C: 1800r/min
D: 3600r/min
```
B: 1200r/min
36
```
In a squirrel cage motor, the current induced has its largest value when the motor
A: is at standstill
B: is just starting
C: has reached its highest torque
D: has reached its highest speed
```
B: is just starting
37
With regard to a squirrel cage motor, the current
A: remains constant as motor speed increases
B: increases sharply as the motor approaches its full rated speed
C: drops sharply as the motor approaches it’s full rated speed
D: remains constant as the motor speed decreases
C: drops sharply as the motor approaches it’s full rated speed
38
```
When a squirrel cage motor is connected directly to the plant distribution
A: manual started may be used
B: a magnetic starter may be used
C: a and b
D: neither a or b
```
C: a and b
39
With regard to a squirrel cage motor, when the voltage is reduced to start the motor, the
A: current is increased, but the machines torque is reduced
B: current is also reduced , but the machines torque increases
C: current is increased and so is the machines torque
D: current is also reduced, and so is the machines torque
D: current is also reduced, and so is the machines torque
40
```
Split phase motor often use ___________ to disconnect the starting windings from the power line
A: centrifugal switch
B: capacitive switch
C: an inductive switch
D: non of the above
```
A: a centrifugal switch
41
```
__________ starting is the simplest of all starting methods
A: across the line
B: autotransformers
C: wye-delta
D: part windings
```
A: across the line
42
```
The starting windings of single phase motors is disconnected when the motor reaches at about __________ precent of its rates speed
A: 45
B: 55
C: 65
D: 75
```
D: 75
43
```
The most popular motor used in North American industry is
A: the synchronous motor
B: the servo motor
C: three phase squirrels cage motor
D: the wound rotor motor
```
C: three phase squirrel cage motor
44
```
The initial in rush current of a motor is comparable to
A: the fla
B: locked rotor current
C: no load amps
D: all of the above
```
B: locked rotor current
45
```
Plugging controls provide for the
A: rapid stop of motor rotation
B: quick reversal of motor rotation
C: a and b
D: neither a or b
```
C: a and b
46
```
Another term for plugging switch
A: start/stop/reversal switch
B: on/halt/reverse switch
C: push/pull switch
D: zero speed switch
```
D: zero speed switch
47
```
Plugging switches are designed to be added to control circuits as
A: feeder devices
B: actuators
C: pilot device
D: contact devices
```
C: pilot device
48
```
Most machines in which plugging is done are driven by
A: linear motor
B: squirrel cage motors
C: ac motors
D: dc motors
```
B: squirrel cage motors
49
The shaft of a plugging switch is most often connected
A: electrically to the motor shaft on the machine it controls
B: electronically to motor shaft on the machine it controls
C: mechanically to the shaft on the machine it controls
D: pneumatically to the shaft on the machine it controls
C: mechanically to the shaft on the machine it controls
50
```
The rotating motion of a motor is transmitted to plugging switch contacts either by a magnetic or by
A: centrifugal mechanism
B: capacitive reactance
C: inductive reactance
D: thermal reactance
```
A: centrifugal mechanism
51
```
A plugging switch acts as a link between a motor and a
A: reversing starter
B: normally close stop button
C: normally open stop button
D: overload switch
```
A: reversing starter
52
```
In a plugging device, to operate the torque and insure that the contacts open and close at the proper time regardless of motor speed, a
A: clutch plate is used
B: set screw is used
C: adjustable contact spring is used
D: rotating cup is used
```
C: adjustable contact spring is used
53
```
A plugging switch must be driven by a
A: negative means
B: open means
C: closed means
D: positive means
```
D: positive means
54
```
Which is not a preferred method of driving a plugging switch
A: gearing
B: chain driven
C: direct flexible coupling
D: belt driven
```
D: belt driven
55
```
In determining the direction of motor rotation, the electrician will connect motor leads at the
A: source
B: transformer
C: control switch bank
D: motor
```
D: motor
56
```
To protect people, machines, and production processes a
A: lockout relay is used
B: latching relay is used
C: Time delay relay is used
D: lockable disconnect switch is used
```
A: lockout relay is used
57
A starter used for a plugging switch will
A: interchange two leads for a 3 phase motor
B: reverse of the armature for a dc motor
C: reverse the windings for a 1-PH motor
D: all of the above
D: all of the above
58
```
When a device prevents the application of a counter torque until the motor speed is reduced to an acceptable value it is known as
A:anti plugging
B: plugging
C: locking out
D: compensating
```
A: anti plugging
59
```
The most accurate method of plug stopping a motor is a
A: one speed switch
B: rotating switch
C: zero speed switch
D: resistor
```
C: zero speed switch
60
```
Three main methods of breaking a motor are
A: coasting, mechanical, dynamic
B: mechanical, coasting, plugging
C: mechanical, dynamic, plugging
D: coasting, dynamic, plugging
```
C: mechanical, dynamic, plugging
61
What are the two basic classifications of timers?
Mode A and mode D
62
Name two methods used by electronic timers to obtain their time base.
RC timer constant and quartz clocks
63
```
With reactor or primary resistor type starter, reactor or resisters are
A: connected in parallel with the motor
B: connected in series with the motor
C: connected in parallel with CR
D: connected in series with a TR
```
B: connected in series with the motor
64
In regards reactor or primary resistance starting; a start under load (as opposed to no load) will result in a
A: longer acceleration time to full speed and longer initial inrush current period
B: longer acceleration time to full speed and shorter initial inrush current period
C: shorter acceleration time to full speed and longer initial inrush current period
D: shorter acceleration time to full speed and shorter initial inrush current period
A: longer acceleration time to full speed and longer initial inrush current period
65
It is desirable to limit the starting current of a motor if full voltage starting causes serious line disturbances on
A: lighting circuits
B: circuits supplying computers and other electronics
C: circuits supplying fire alarms, security system, etc
D: all of the above
D: all of the above
66
Large current inrush during the starting of a large motors may cause
A: the control circuit to change
B: utility line disturbance and damage to machines due to over torque
C: excess motor speed
D: all of the above
B: utility line disturbance and damage to machines
67
Closed transition starting means that the motor is
A: momentarily disconnected at the beginning of the starting cycle
B: momentarily disconnected at the end of the starting cycle
C: connected to the line only when full voltage is applied
D: never disconnected from the line from the moment it is first connected until the motor is operating at full voltage
D: never disconnected from the line from the moment it is first connected until the motor is operating at full voltage
68
```
There are conditions where it is not acceptable to start a motor across the line due to excessive
A: starting current of torque
B: size of equipment
C: acceleration time
D: cost of equipment
```
A: starting current to torque
69
```
The rate of a rise of current in a circuit is __________ circuit s
A: immediate in resistive
B: always constant in AC
C: at an exponential curve in inductive
D: both a and c
```
D: both a and c
70
```
If the motor is disconnected from the line between the start and run stage, the starting method is referred to as
A: a transition type
B: an open transition
C: a closed transition
D:a corrupt transition
```
B: an open transition
71
```
Most motors are successfully started at
A: 25%
B: 50%
C: 65%
D: 80%
```
C: 65%
72
```
Both primary resistor ans reactor starters are available for use on
A: single phase reversing operations
B: three phase reversing operations
C: a and b
D: neither a or b
```
C: a and b
73
```
Some circuits may use several steps of starting because of
A: limitation by the utility
B: torque limits of a machine
C: length of acceleration time desired
D: all of the above
```
D: all of the above
74
```
Starting transistors are considered
A: resistive loads
B: inductive loads
C: capacitive loads
D: all the above
```
B: inductive loads
75
```
Autotransformers used as a reduced starter must have a minimum of
A: two taps
B: three taps
C: four taps
D: six taps
```
A: two taps
76
```
Autotransformers starters are generally employed to start _______ type motors
A: synchronous
B: squirrel cage
C: non induction
D: wound rotor
```
B: squirrel cage
77
Motors started with autotransformers reduced voltage starters draw
A: less current and develops less torque than when connected to line voltage
B: less current and develop more torque than when connected to line voltage
C: more current and develop more torque than when connected to line voltage
D: more current and develop less torque than when connected to line voltage
A: less current and develops less torque than when connected to line voltage
78
```
_____________ are often used to sense the current of large motors
A: current resistors (CR’s)
B: current varistors (CV’s)
C: current capacitor (CC’s)
D: current transformers (CT’s)
```
D: current transformers (CT’s)
79
```
Some resistors and reactors starters use multiple steps of starting. This is accomplished by tapping the resistor or reactor to provide different values
A: resistance or capacitance
B: frequency or resistance
C: resistance or inductive reactance
D: capacitance or inductive reactance
```
C: resistance or inductive reactance
80
When an auto transformer is used as a reduced voltage starter,
A: a fixed timer controls when the motor receives full voltage
B: an adjustable timer controls when the motor receives full voltage
C: a fixed counter controls when the motor receives full voltage
D: an adjustable counter when the motor receives full voltage
B: an adjustable timer controls when the motor receives full voltage
