# E&I questions

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1. state ohms law
E=IxR
2. what is impedance stated as?
z or resistance
3. what effects must be known before calculating impedance?
resistance
4. state the formula for calculating power
P=IxE
5. power is defined as_____
the rate of doing work
6. describe turns ratio of a transformer
it determines the secondary voltage
7. like magnetic poles_____each other
repel
8. what instrument measures integrity of insulation of a winding?
megger
9. what units are used when measuring integrity of a winding?
ohms
10. if a transformer has 4 to 1 ratio with 480v applied to the primary, what is the secondary voltage?
120v.   voltage divided by turns ratio
11. how is a dry transformer cooled?
with air
12. why cant water be used for cooling a liquid cooled transformer?
no diaelectric, capacitance and no resistance
13. how is a battery created?
2 or more cells connected together
14. describe a series connection
they are all in a line
15. describe a parallel connection
they are stacked
16. if four 1.5v cells are connected in series, what is the resulting voltage?
6v
17. what test instrument is used to test potential difference?
voltmeter
18. define potential difference.
it is the difference in potential energy per unit of charge between 2 pts
19. what is the oppostion to current flow called?
resistance
20. describe a solenoid
it works off an electromagnet
21. can a solenoid be used as a control device?
yes, on/off control
22. what is the insulating material used in any electrical device called?
diaelectric
23. name 4 good conductors
copper, aluminum, water, metal
24. name 4 good insulators
plastic, fiberglass, rubber, silicon
25. a complete cycle of an ac circuit consists of _____ degrees
360
26. what is the U.S. standard measure of rate for elecrical power?
watts
27. describe the difference between primary and secondary storage cells.
secondary cells can be recharged
28. what liquid can be put into a battery? why?
elecrolyte, because it is a good conductor
29. what is the density of a material compared to density of water?
specific gravity
30. what is the S.G. of water?
1
31. what does it mean if a battery has a 10 amp hour rating?
it will draw 10 amps for 1 hour
32. what determines the capacity of a battery?
the size and the number of plates
33. should batteries be vented when charging?
yes
34. what is the elecrolyte in a lead acid battery?
water and sulfuric acid
35. where is a 4way switch used?
where there is more than 2 switches needed in 1 location for controlling 1 light
36. what does the simplist type of capacitor use for its diaelectric?
air type or paper type
37. what should be done to a capacitor removed from a circuit?
it should be shorted and discharged
38. what is the symbol for inductive reactance?
XL
39. all the power in a circuit is consumed by the wiring...
false
40. how many degrees are windings of a 3 phase motor separated?
120 degrees
41. what metal is usually used to construct small transformer coils?
copper
42. if an iron core is inserted into a copper core, the magnetic field is increased
43. a transformer has 4000 turns in the primary coil, and 400 turns in the secondary. what is the secondary voltage if 120 volts is applied to the primary?
12v. voltage of primary times turns of secondary divided by turns of primary
44. _____voltage is required to run a synchronous motor.
AC and DC
45. the rotor winding of a large synchronous motor is energized with ____voltage.
DC
46. how is speed of 3 phase induction motor varied?
by the number of poles or VFD
47. name the parts of a diode.
anode and cathode
48. what is the test that measures relationship in ohms of each winding of a 3 phase motor to each other?
bridging
49. what is a bridge rectifier used for?
converting AC to DC
50. how does an elecrical relay work?
it consists of a magnet armature mounted over an elecromagnet that receives voltage to change position of contacts
51. what are fuses for?
to protect the wire
52. what does AWG represent?
american wire gauge
53. when is arching more prevalent, starting or stopping a motor?
stopping
54. what is another name for a melting alloy overload?
eutectic melting alloy
55. why is control circuit voltage usually lower than power circuit?
you dont want high voltage close to pushbuttons
56. how are locations of elements of a schematic referenced to other diagrams?
they are under the element on a schematic
57. what does TEFC on a motor tag mean?
Totally Enclosed Fan Cooled
58. what motors are used in a class I division II area?
TEFC
59. how are AC ammeters connected?
60. how are voltmeters connected?
61. what determines wire size?
the current used
62. which ranges of pressure are manometers commonly used to measure?
low pressures, psi and inches of water
63. which conditions will damage a pressure element?
high pressure
64. pressure transducers receive information in terms of pressure and convert that information to?
electrical signal, or ma
65. fluid flowing through a pipe exerts pressure in which direction?
all directions
66. as velocity of fluid in a pipe increases, what does the pressure on the pipe wall do?
it decreases
67. the quantity of fluid passing a given point in a specific period of time is the expression of?
flow
68. a hollow tube that can be installed in a pipe with one end open to incoming flow and the other measuring the pressure of flow is ?
peto tube
69. what can be determined when the area of a fluid and the velocity are known?
rate of flow
70. which output signals are associated with electronic control systems?
voltage and current
71. what signal is generated when the junction of two dissimilar metals are heated?
millivolts
72. what will happen to the resistance of a sensing element if the temperature of an RTD is increased?
it will increase
73. what is commonly used in fluid temp thermometers and why?
mercury. it expands and contracts at a constant rate
74. which section of a typical positioner automatically determines the position of an actuator?
feedback
75. what must all control loops have?
inputs and outputs
76. what control functions are used to determine if certain operating conditions are met?
logic functions
77. what are the series of mathmatical steps that a controller is programmed to follow?
control algorithm
78. what is the device that continually compares the value of process variable to the set point?
controller
79. the tubing of the high side of a transmitter for flow measuring should face?
the upstream of the orifice
80. which control mode is used alone or in combination with other modes?
proportional
81. in a cascade control system, what does the primary controller do?
set the set point for the secondary or slave controller
82. what are some parts of a photo electric control system?
83. what would the reading be on a delta P instrument with condensed vapor on the low side?
low zero or below zero
84. a binary number of 0000111 is equal to?
7
85. what is the midpoint range for a pneumatic system?
9 psi
86. according to ohms law, if the voltage across a resistor is doubled, what happens to the current?
it too is doubled
87. the best way to check accuracy of a temp thermocouple is with ______
a temperature bath
88. what is optional in a single variable control loop?
a recorder
89. how can parallax error be reduced?
with a mirror
90. which signal might a digital device receive if a switch closes?
1 or closed
91. accuracy requirementss for measurement differ according to the _____
process
92. which element would you use for the lowest pressure and vacuum measurement?
a diaphragm
93. an advantage of the RTD over the thermistor is ______
the RTD's higher temperature
94. air supply for a pneumatic transmitter is typically_____
20 psi
95. a single data highway uses two cables to provide _____
redundance
96. libraries of _____ are provided for common control functions like PID
algorithms
97. a reset of 5 repeats per minute is equal to an integral time of______
12 seconds per repeat
98. which part of the liquid filled capillary system is usually the only part exposed to the process?
the bulb
99. list examples of control elements...
valves, motors, relays, solenoids
100. what is the most important consideration in a loop control?
dynamics of process
101. a disturbance within a control loop is corrected by _____
feedback
102. flashing and cavitation in valves often result in _____
failure
103. where are PLC's best used?
where quick response is needed
104. all automatic controllers compare _______
process variables to set point
105. an inductive proximity sensor can be used to detect _____
ferrous metals
106. a logic AND circuit can be represented by 2 or more sets of ___ contacts in series
normally closed
107. the temperature range of a thermocouple depends on the _____
2 metals
108. the interface device that connects a computer to a network is known as a _____
gateway
109. a major advantage of digital over analog data trasmission is _____
less noise and faster transmission
110. what is the most important part of hardware documentation for a troubleshooter?
electrical schematics
111. what is one of the main disadvantages of pneumatic control?
lag time
112. if transmitter_____is known, _____ can be calculated
input variable ; output
113. gain is the inverse formula of _____
proportional band
114. how many values can a 3 bit binary number represent?
8
115. the accuracy of conversion from sensor output to useful PV data depends largely on ______
the linearity of the sensor
116. what does proportional action ask?
how big is the error
117. what is parallax error?
it occurs when reading a gauge at an angle
118. thermocouple positive wire is usually_____
white
119. a typical ouput of a strain gauge bridge circuit is_____
10 to 100 mv
120. what is the phase to phase voltage of a delta system?
equal
121. what is the phase to phase voltage of a wye system?
it is 2 times the neutral voltage
122. how are switches defined and categorized?
by the number of poles and throws
123. ladder diagrams are known as elementary diagrams
124. how are contacts of a drum switch manipulated?
rotation of the switch
125. drum switches are capable of handling currents larger than normal pilot devices
126. what are limit switches composed of?
actuator and contacts
127. what are the 2 most common types of proximity switches?
inductive and capacitive
128. what are 2 types of starter motors?
manual and magnetic
129. the first thing to do when troubleshooting relays is_____
check for voltage
130. why are overload relays used?
to protect the motor
131. how are seal in contacts placed relative to start button contacts?
parallel
132. what configuration do push buttons usually come in?
normally open and normally closed
133. which starter is operated by a coil inside the contactor?
magnetic starter
134. what are AC motors primarily composed of?
stator, rotor, and end plates
135. what are the 3 basic parts of a DC motor?
frame, end plates and armature
136. what determines the speed of an AC induction motor?
the # of poles... more poles make less speed and more power. less poles make more speed and less power.
137. what are the 2 windings of a single phase motor?
run and start
138. if poles are removed from an AC motor, speed and horsepower will NOT increase
139. how do you change rotation on a 3 phase motor?
swapping 2 leads or using a drum switch
140. what would happen to a single phase AC motor if run winding and start winding were left energized?
they would burn up
141. what is the opposition of electron flow in a DC circuit?
resistance
142. what is an AC wave form called?
sine wave

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 Author: motodaddie ID: 220821 Filename: E&I questions Updated: 2013-05-24 20:26:18 Tags: test Folders: Description: E&I questions Show Answers:

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