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3E051 Set C Book 3
| Question | Answer |
|---|---|
| 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
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