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Midterm Review Flashcards

1
Q

What type of metal remains in a liquid state at room temp

A

Mercury

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2
Q

What two factors determine the amount of voltage produced by a thermocouple

A

Type of material, temperature difference of the junctions

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3
Q

What is a thermopile

A

Thermocouples connected in series

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4
Q

What does RTD stand for

A

Resistance temperature device

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5
Q

What type of wire is used to make an RTD

A

Platinum

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6
Q

What type of material is a thermistor made of

A

Semi-conductive

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7
Q

If temperature increases in a silicon diode will voltage drop increase or decrease

A

Decrease

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8
Q

What type of chemical is used to cause a pressure change in a bellows type thermostat

A

Refrigerants

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9
Q

What material was used to make the first hall generator

A

Gold

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10
Q

What two factors determine the POLARITY of the output voltage produced my the hall generator

A

1.) direction of current flow
2.) polarity of the magnetic field

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11
Q

What two factors determine the amount of VOLTAGE produced by the hall generator

A

1.) Amount of current
2.) strength of current

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12
Q

A ferrous metal disc used to shunt a magnetic field

A

A reluctor

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13
Q

In a hall generator is the voltage produce A/C or D/C

A

D/C

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14
Q

What type of electric circuit is used to increase the sensitivity of a proximity detector

A

Tank circuit

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15
Q

What type of proximity detector uses an oscillator that operates at radio frequencies?

A

All-metal detector

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16
Q

Two types of proximity detectors used to detect objects not made of metal

A

Capacitive proximity, ultrasonic proximity

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17
Q

What is the maximum range that most proximity detectors can be used to sense an object

A

25mm (1”)

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18
Q

Three major categories of photo detectors

A

Photovoltaic, photoemmisive, photo-conductive

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19
Q

Which category of photodetectors does the solar cell belong

A

Photovoltaic

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20
Q

Which category of photodetectors does the cad cell belong

A

Photo conductive

21
Q

The term cad cell is a name for what device

A

Cadmium sulfide cell

22
Q

What is the function of the transmitter in a photodetectorunit

A

The light source

23
Q

What is the advantage of a photodetector that uses a reflector

A

Need electrical connection at only one pice of equipment

24
Q

How much voltage does a silicon solar cell produce

25
What determines the amount of current a solar cell produces
The surface area of the cell
26
What is the operating voltage of most magnetic control systems
120v
27
How many primary windings do control transformers have
2
28
How are the primary windings connected to operate on a 240v system
Parallel
29
How are the primary windings connected on the control transformer to operate at 240v
Parallel
30
How are the control transformer windings connected to operate at 480v
Series
31
Why are two primary leads crossed on a control transformer
To make connection to the primary winding easier
32
Two basic classifications of timers
On delay, off delay
33
How are pneumatic timers adjusted
Adjusting the needle valve
34
Two methods used by electronic timers to obtain their time base
RC time constant Quartz clock
35
What is meant by the statement that solenoid valves are digital devices
They are completely on or completely off
36
What type of valve is generally used to supply air pressure to a DOUBLE acting cylinder
Four-way
37
What two sections are generally used to operate motor operated valves
Local and remote
38
What type of switch is used to ensure a motor operated valve is tightly seated
A torque switch
39
3 methods of braking a motor
Mechanical, dynamic, plugging
40
What type of braking is used on cranes
Mechanical
41
The Amount of counter torque produced by a dc generator is proportional to what?
Armature current
42
How is braking time controlled when using dynamic braking
Adjusting the resistance value
43
How is plugging accomplished
Momentarily disconnect power. Momentarily reverse the motor
44
What device is used to stop a motor when plugging is used
0 speed switch
45
What two electrical components are connected in series with a motor to limit starting current
Resistors and reactors
46
Does resistive or reactive current rise at an exponential rate
Reactive
47
What three percentages of line voltage do auto transformers permit to the motor during starting
50,65,80
48
Closed transition
Ensures motor is never disconnected from line voltage until the motor is at full voltage

Motor Controls (1 decks)

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