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3E051 Set C Book 3

QuestionAnswer
A meter in an electrical circuit measures electrical properties
when using a voltmeter to measure an unknown voltage, which range do you select? Highest
Polarity must be observed when measuring coltage in Direct current (DC) circuits
To improve the sensitivity of a reading when you connect a voltmeter to an energised circuit and it indicates only a small needle movement, change the selector knob to a lower range
A full-scale reading on an ohmmeter is zero
What output voltages are produced when you operate the crank of a megohmmeter? 500 to 1,000 volts
Which meter measures current flow in an electrical circuit? Clamp-on ammeter
How many conductors must a clamp-on ammeter encircle to obtain an accurate current reading? one
Which phase sequence would cause a motor to spin in the opposite direction of the other three? C-B-A
What is the normal time frame, in hours, for operating a recording meter? 24 hours
When the rotation per minute of a motor using a stroboscope tachometer is adjusted, the pattern appears to stand still
What meter is used to locate higher-than-normal temperatures of conductors and electrical connections? infrared detector
What tester is used to verify the atmospheric condition inside a manhole before you enter? Gas detector
What is the voltage range os a high-voltage phase tester? 2.3 kV to 80 kV
A hot stick must be tested with a hot stick tester at intervals not to exceed 6 months
What is the maximum ohmic reading for static grounds according to current Air Force directives? 10,000
What is the maximum ground resistance value for an electrical system with a voltage of 600 VAC or less? 25 ohms
Which of the following is frequently used to limit ground fault current to a manageable level in circuits of 1 kV to 15 kV Resistor or reactor
What type of ground rod is most often used for grounding electrical systems? Copper-clad steel
Which items are not parts of the lightening protection system? Electrolytic plates
What is the approximate percentage of the total resistance that can be found within on foot of a ground rod? 68
Which is the preferred method of obtaining a better ground? Deeper ground rod penetration
Which article of the National Electrical Code covers grounding? Article 250
A system neutral conductor is likely grounded improperly (grounded on the side of the service enterance disconnect), if the ohmic value is less than 20K
At what intervals should a wye-connected distribution system neutral be grounded? At a distance not to exceed 1/4 mile
The metal frame of a building can be used as a facility ground if the frame is effectively grounded.
What are the minimum requirements for the depth and length of a facility ground ring? 2 1/2 feet deep; 20 feet long
What are the requirements for a facility ground rod? 8 feet long; copper-clad steel
Which problem is eliminated by computer grounding? Noise pickup and high-frequency
Which grounding systems are needed for the grounding of computer equipment? power distribution and a reference grounding system
Isolated ground receptacles are used in circuits feeding electronic devices to reduce noise
In an isolated ground (IG) receptacle, the grounding pin is purposely insulated from the outlet box
What happens if a bare spot on the hot conductor touches the inside of a properly grounded outlet box? The circuit breaker for that circuit trips
Physical failure of grounding systems usually occurs in which portion of the system? Just above and below ground level
How must an isolation transformer be grounded to the transformer enclosure? Shield and core grounded to the enclosure
Which of the following is not an effect of ground-neutral reversal in an interior wiring system? A higher phase to neutral voltage
The process of separating air molecules into positive ions and negative electrons is called ionization
A main counterpoise is installed at a minimum depth of how many inches? 24
The main counterpoise is installed beyond the building perimeter at not less than 3 nor more than 8 feet
Lightning grounds are designed to handle high current
What is the minimum size grounding conductor used for hazardous locations? No. 1/0 AWG
The maximum spacing, in feet, between air terminals is 25
What is the minimum radius, in inches, that lightning protection conductors bend? 8
Grounding of lightning protection systems should conform to NFPA 780
Bonding to other systems includes all water pipes, well casings, and other conductive objects within how many feet of the grounding system? 25
What is the minimum size copper wire used to connect different grounding systems? 6 AMG
What size grounding rods are used in a lightning protection system? 10 feet in lenth, and a 3/4-inch diameter
When ground rods are used with a counterpoise, how deep are ground rod tops driven? To same elevation as counterpoise below finished grade.
What is the minimum depth, in inches, below the earth's surface that a counterpoise will be installed around a facility? 24
The shortest length a radial system of grounding conductors extend away from a grounding connection is not less than 12 feet long
What are the properties of good insulators? Clean dry surfaces in low humidity; can hold their charge.
What is the minimum sparking voltage generally accepted for the shortest measurable length of gap? 350 volts
At what voltage can a static charge ignite gasoline? 1500 volts
Unwanted electrical charges in hazeardous areas are dissipated by using a continous electrical path to ground.
Which size copper wire is used to bond conductive objects when they are not concealed or mechanically protected? No. 6 AWG copper wire.
On above ground fuel tanks that rest on the earth, ground rods are required if the resistance to earth exceeds 10,000 ohms
If an above ground fuel tank is to be grounded, what size and type-grounding conductor must be used? 1/4 to 3/8-inch galvanized guy wire
If an above ground fuel tank is to be grounded, what size and type of ground rod must be used? 5/8-inch by 8-foot galvanized steel
If a fence has a 2,400-volt overhead line crossing over it, ground the fence at a distance not to exceed 150 feet on each side of the line crossing
With what type of conductor must a fuel storage area fence and gate be bonded? flex braid copper
If railroad tracks extend to within 100 feet of fuel dispensing stands, the rails are bonded together and grounded
What length, type of material, and to what depth must a ground rod be driven for a static ground at a fuel dispensing hydrant? 8-foot galvanized-steel rod driven 2 inches below the surface of the apron
What size stranded copper bonding cable must be used to bond driven ground rods for hydrant outlets? No. 1/0 AWG
Static grounds for aircraft hangar floors must have an ohmic resistance of 25 ohms or less when the static ground is connected to the hangar's electrical system ground
What is the minimum siaze ground rod that can be used in a hangar floor? 3/4 inch by 2 feet
How many grounding receptacles per aircraft space are used in hangars that house a specific number and type of aircraft? one
How often are liquid fuel maintenance personnel required to check grounding systems for fill stands and fuel dispensing areas? monthly
What needs to be done if fuel maintenance personnal find excessive amounts of corrosion on ground connections? cathodic protection
What are the minimum size requirements for a ground rod used for lightning protection? 3/4 inch diameter by 10 foot length
What is the minimum size conductor that is used for a ground loop? No. 1/0 AWG
What is the minimum size copper conductor that can be used for lightning protection in an overhead wire system? No. 6 AWG
For lightning protection, air terminals near vents that emit explosive gas must be at least how many feet long and extend at how many feet above the vent? 15 feet long, 5 feet above the vent
What is the minimum number of down conductors that are used to provide lightning protection to a facility? 2
What type of grounding system must be installed when ground rods cannot be driven due to the soil condition? Radials
What are the grounding requirements for a facility that handles explosive materials? statice, equipment, and lightning ground subsystems are tied together
What is the maximum ohmic requirement for a military communication facility ground subsystem? 10
The approximate ohmic resistance of two parallel ground rods approximately 20 feet apart is about what percent of the resistance of one rod? 60
A fence must be grounded to a communication facility's electrode eubsystem if its proximity to that subsystem is within how many feet? 6
Which ratio is the required "zone of protection" for communication facilities? 1:1
A pole supporting overhead ground wires must provide clearance above the highest part of the facility of at least 6 feet
The minimum number of inches the radius of a bend in a down conductor can have is 8
What is the main disadvantage of a valve-type arrester? slow reaction time
Which wire is used for fault protection of a facility? green insulated
A tower and a communication facility must be enclosed by the same ground loop if they are spaced no farther apart than 20 feet
A visual inspection should detect all of the following except the presence of voltage in the circuit
What information must be recorded when testing and inspecting grounding systems? deficiencies found, corrective action and date of repair
What instruments are used when testing grounding systems? Fall-of-potential meter and digital ohmmeter
What is the frequency required for visual, continuity and resistance checks for hazardous explosive areas (weapon storage)? every 7 months for visual inspection; every 14 months for continuity and resistance test
Created by: melissafish