All handouts Flashcards
When using in an industrial sensing application, a heated metal will A: contract B: expand C: melt D: none of the above
B: expand
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
C: different expansion rate
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
C: a and b
A metal that remains in a liquid stage at room temperature is A: Copper B: brass C: tin D: mercury
D: mercury
A RTD is made of A: Copper wire B: platinum wire C: chrome wire D: iron wire
B: platinum wire
A bellows type thermostat works on a change in A: heat principals B: movement principles C: resistance principles D: pressure principles
D: pressure principles
A device that heats two dissimilar metals to produce a voltage is known as a A: thermostat B: thermometer C: thermoreactor D: thermocouple
D: thermocouple
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: thermopile
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: resistance temperature detector
Thermistors exhibit a \_\_\_\_\_\_\_\_\_\_ change of resistance at a certain temperature A: rapid B: linear C: gradual D: a and b
A: rapid
A hall generator is constructed as a A: coiled device B: vacuum device C: capacitive device D: integrated device
D: integrated device
Materials used to shunt a magnetic field away from objects is known as a A: detector B: reactor C: pulser D: reluctor
D: reluctor
Proximity detectors are basically A: light detector B: heat detector C: metal detector D: all of the above
C: metal detectors
Proximity detectors will more easily detect \_\_\_\_\_\_\_ because it is ferrous A: copper B: iron C: brass D: aluminum
B: iron
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
C: a magnetic field
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
D: all of the above
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: far away from each other as possible
A proximity detector that detects non-metallic objects operate in a change in A: resistance B: capacitance C: inductance D: impedance
B: capacitance
Most capacitive proximity detectors can sense the presence of A: wood B: copper C: brass D: all of the above
D: all of the above
Most capacitive proximity detectors have a range of approximately A: 5mm B: 10mm C: 25mm D: 100mm
C: 25mm
Ultrasonic detectors have a wide range of adjustable A: frequency B: sensing speed C: sensing distance D: physical size
C: sensing distance
Ultrasonic detectors emit a A: low frequency sound B: high frequency sound C: low frequency radio wave D: high frequency radio wave
B: high frequency sound
Photodetector detect A: sound B: mechanical motion C: light D: heat
C: light
Compared to most other photodetector, a photoemissive device are a A: more reliable device B: slower device C: smaller in size D: faster device
D: faster device
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
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
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
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
Squirrel cage induction motos are characterized by A: simplicity B: ruggedness C: reliability D: all of the above
D: all of the above
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
The part of a squirrel cage motor that remains stationary is called the A: shaft B: armature C: rotor D: stator
D: stator
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
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
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
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
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
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
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
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
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
\_\_\_\_\_\_\_\_\_\_ starting is the simplest of all starting methods A: across the line B: autotransformers C: wye-delta D: part windings
A: across the line
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
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
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
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
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
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
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
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
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
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
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
A plugging switch must be driven by a A: negative means B: open means C: closed means D: positive means
D: positive means
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
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
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
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
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
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
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
What are the two basic classifications of timers?
Mode A and mode D
Name two methods used by electronic timers to obtain their time base.
RC timer constant and quartz clocks
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
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
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
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
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
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
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
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
Most motors are successfully started at A: 25% B: 50% C: 65% D: 80%
C: 65%
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
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
Starting transistors are considered A: resistive loads B: inductive loads C: capacitive loads D: all the above
B: inductive loads
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
Autotransformers starters are generally employed to start \_\_\_\_\_\_\_ type motors A: synchronous B: squirrel cage C: non induction D: wound rotor
B: squirrel cage
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
\_\_\_\_\_\_\_\_\_\_\_\_\_ 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)
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
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
