Mississippi Master Electrician Examination

A 480-volt, three-phase feeder on a Mississippi commercial job supplies a balanced load of 75 amperes at a lagging power factor of 0.90. Using √3 = 1.732, what is the real power of this load?

• A56.1 kW
• B62.4 kVA
• C32.4 kW
• D36.0 kW

A 60 Hz series circuit contains 12 ohms of resistance, 16 ohms of inductive reactance, and 7 ohms of capacitive reactance. What is the total impedance?

• A35 ohms
• B15 ohms
• C21 ohms
• D9 ohms

A 112.5 kVA, three-phase transformer has a 480-volt primary and a 208Y/120-volt secondary. Using √3 = 1.732, what is the secondary full-load line current?

• A135 A
• B541 A
• C312 A
• D208 A

A 480-volt, three-phase circuit carries 90 amperes for 180 feet on copper conductors. Use K = 12.9, √3 = 1.732, and a circular-mil area of 83,690 CM for 1 AWG. What is the voltage drop?

• A5.0 V
• B7.5 V
• C2.5 V
• D4.3 V

What is the peak (zero-to-peak) value of a 277-volt RMS sinusoidal line-to-neutral voltage? Use √2 = 1.414.

• A391.7 V
• B277.0 V
• C196.0 V
• D783.4 V

A purely resistive 240-volt heater has a resistance of 16 ohms. What current does the heater draw, and what is its power?

• A16 A and 3,840 W
• B15 A and 3,600 W
• C12 A and 2,880 W
• D20 A and 4,800 W

A three-phase motor load measures 40 kW of real power and 50 kVA of apparent power. What is the power factor, and what is the reactive power?

• A0.80 lagging and 10 kVAR
• B1.25 leading and 30 kVAR
• C0.80 lagging and 30 kVAR
• D0.64 lagging and 40 kVAR

Two 20-ohm resistors are connected in parallel, and that combination is in series with a 15-ohm resistor. The circuit is supplied at 100 volts DC. What is the total current?

• A2.0 A
• B6.7 A
• C1.8 A
• D4.0 A

Using the NEC 2020 standard calculation, a 2,800-square-foot dwelling has a general lighting unit load of 3 VA per square foot, two small-appliance branch circuits, and one laundry branch circuit. After applying Table 220.42 dwelling demand (first 3,000 VA at 100 percent, remainder at 35 percent), what is the demand-loaded general lighting and receptacle load?

• A6,465 VA
• B12,900 VA
• C8,400 VA
• D4,515 VA

A feeder supplies an 80-ampere continuous load and a 50-ampere noncontinuous load. Per NEC 2020 215.2(A)(1) and 215.3, what is the minimum ampacity and overcurrent-device rating basis for that feeder?

• A130 A
• B150 A
• C163 A
• D100 A

What is the NEC 2020 minimum number and rating of small-appliance branch circuits required to supply receptacle outlets in the kitchen, pantry, breakfast room, and dining room of a dwelling unit?

• AOne 20-ampere circuit
• BTwo or more 15-ampere circuits
• CTwo or more 20-ampere circuits
• DOne 15-ampere and one 20-ampere circuit

In a dwelling unit, receptacle outlets serving habitable-room wall space must be installed so that no point measured horizontally along the floor line of any wall space is more than which distance from a receptacle outlet?

• A12 feet
• B4 feet
• C2 feet
• D6 feet

For dwelling-unit kitchen countertop receptacles, no point along the wall line may be more than which distance from a receptacle outlet, measured horizontally?

• A24 inches
• B12 inches
• C18 inches
• D36 inches

Per NEC 2020 230.24(B)(4), what is the minimum vertical clearance above a public street, alley, road, or parking area subject to truck traffic for 120/240-volt service-drop conductors?

• A12 feet
• B18 feet
• C15 feet
• D10 feet

Under NEC 2020 230.71, which statement correctly describes the maximum number of service disconnects?

• AUp to six switches or sets of circuit breakers may still be installed as the service disc…
• BA service may have an unlimited number of disconnects if each is labeled
• CEach service shall have only one disconnecting means unless 230.71(B) permits two to six…
• DA service is limited to two disconnects in all cases

NEC 2020 210.11(C)(4) requires which branch circuit for the receptacle outlets required by 210.52(G)(1) in an attached dwelling-unit garage?

• AAny 15-ampere general lighting circuit that also serves the garage lights
• BA 30-ampere, 240-volt circuit shared with the electric dryer
• CNo dedicated circuit is required if GFCI protection is provided
• DAt least one 120-volt, 20-ampere branch circuit that has no other outlets, except a permi…

A single household electric range is nameplate-rated 14 kW, 240 volts. NEC 2020 Table 220.55 Column C lists 8 kW for one range not over 12 kW, and Note 4 increases that demand 5 percent for each kilowatt the nameplate exceeds 12 kW. What demand load is used in the standard service calculation?

• A8.8 kW
• B14.0 kW
• C8.0 kW
• D11.2 kW

A one-family dwelling is calculated under the NEC 2020 optional method of 220.82. The general loads (lighting, receptacles, appliances, dryer, range, and water heater) total 24,000 VA. Cooling is 6,000 VA and is larger than heating. What is the optional-method demand load?

• A30,000 VA
• B21,600 VA
• C15,600 VA
• D24,000 VA

A multiwire branch circuit supplies a 120/240-volt split-wired duplex receptacle. What disconnecting means does NEC 2020 210.4(B) require?

• AA single-pole breaker on only one ungrounded conductor if the neutral is identified
• BNo disconnect other than the service main is required
• CA means that simultaneously disconnects all ungrounded conductors at the point where the…
• DA disconnect only for the grounded conductor

A commercial office is calculated under NEC 2020 220.14(I). Twenty duplex receptacle outlets are each one yoke. Using 180 VA per strap, what is the receptacle computed load before any Table 220.44 demand factor?

• A1,800 VA
• B7,200 VA
• C2,400 VA
• D3,600 VA

NEC 2020 Table 250.66 requires a 4 AWG copper grounding electrode conductor where the largest ungrounded service-entrance conductor is 2/0 or 3/0 AWG copper, and a 2 AWG copper conductor where that service conductor is 4/0 AWG or 250 kcmil copper. For a service supplied by 3/0 AWG copper ungrounded conductors, what is the minimum copper GEC to the grounding electrode system (not a sole rod, pipe, or plate)?

• A4 AWG copper
• B2 AWG copper
• C6 AWG copper
• D8 AWG copper

A service has 500 kcmil copper ungrounded conductors. The only grounding electrode is a driven ground rod. Per NEC 2020 250.66(A), what is the largest copper grounding electrode conductor required to that rod?

• A1/0 AWG copper
• B6 AWG copper
• C2 AWG copper
• D4 AWG copper

A single rod, pipe, or plate grounding electrode is installed for a service. Unless the electrode has a resistance to earth of 25 ohms or less, NEC 2020 250.53(A)(2) requires what?

• AThe service must be ungrounded
• BThe grounding electrode conductor must be increased two sizes
• CIt shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) t…
• DA concrete-encased electrode is prohibited

NEC 2020 Table 250.122 lists the following copper equipment grounding conductors: 100 A → 8 AWG, 200 A → 6 AWG, 300 A → 4 AWG, 400 A → 3 AWG. What is the minimum copper EGC for a 200-ampere feeder overcurrent device when the ungrounded conductors have not been increased in size?

• A8 AWG copper
• B4 AWG copper
• C3 AWG copper
• D6 AWG copper

Which installation qualifies as a concrete-encased electrode under NEC 2020 250.52(A)(3)?

• AAt least 20 feet of 1/2-inch electrically conductive steel reinforcing bar, or at least 2…
• BAny 8-foot ground rod driven beside a footing
• CTen feet of 6 AWG bare copper laid on top of a slab
• DA metal underground water pipe in contact with the earth for 5 feet

NEC 2020 Table 250.102(C)(1) uses the same copper sizes as Table 250.66. For a service with 3/0 AWG copper ungrounded conductors, that table lists 4 AWG copper. What is the minimum copper main bonding jumper?

• A6 AWG copper
• B4 AWG copper
• C8 AWG copper
• D2 AWG copper

A 480-volt delta to 208Y/120-volt wye transformer supplies a building as a separately derived system. Where must the system bonding jumper be installed?

• AAt every panelboard on the secondary
• BOnly at a driven ground rod, never at the transformer
• CAt any single point on the separately derived system from the source to the first system…
• DOn the 480-volt primary only

A 500-ampere feeder uses 500 kcmil copper ungrounded conductors and a 2 AWG copper EGC (66,360 CM). The ungrounded conductors are increased to 750 kcmil for voltage drop. Circular-mil areas: 2 AWG = 66,360; 1 AWG = 83,690; 1/0 AWG = 105,600; 2/0 AWG = 133,100. Per NEC 2020 250.122(B), what is the minimum copper EGC after the proportional increase?

• A2 AWG copper
• B1 AWG copper
• C2/0 AWG copper
• D1/0 AWG copper

NEC 2020 250.104(A)(1) requires the metal water piping system of a building to be bonded to which of the following?

• AThe service equipment enclosure, the grounded conductor at the service, the grounding ele…
• BA ground rod only, using any conductor size
• CThe nearest branch-circuit equipment grounding conductor, regardless of size
• DNo bonding is required if the water service is nonmetallic for the last 2 feet

Unless specifically permitted elsewhere, NEC 2020 240.4(D) limits the overcurrent protection of 12 AWG copper conductors to a maximum of which rating?

• A25 amperes
• B20 amperes
• C30 amperes
• D15 amperes

NEC 2020 Table 310.16 lists these 75°C copper ampacities: 3 AWG = 100 A, 2 AWG = 115 A, 1 AWG = 130 A, 1/0 AWG = 150 A, 2/0 AWG = 175 A, 3/0 AWG = 200 A. What is the Table 310.16 ampacity of 3/0 AWG copper THWN at 75°C before any adjustment?

• A175 A
• B230 A
• C200 A
• D150 A

Six current-carrying 4 AWG copper THHN/THWN-2 conductors are installed in one raceway in a 30°C ambient. NEC 2020 Table 310.16 lists 4 AWG copper as 85 A at 75°C and 95 A at 90°C. Table 310.15(C)(1) requires an 80 percent adjustment for 4 through 6 current-carrying conductors. Using the 90°C column for adjustment, what is the adjusted ampacity?

• A95 A
• B68 A
• C85 A
• D76 A

Eight current-carrying 10 AWG copper THHN conductors are in one conduit. Table 310.16 lists 10 AWG copper as 40 A at 90°C. Table 310.15(C)(1) requires 70 percent adjustment for 7 through 9 current-carrying conductors. What is the adjusted ampacity?

• A28 A
• B40 A
• C24 A
• D35 A

Type NM-B cable contains 90°C conductors. Per NEC 2020 334.80, the ampacity of NM-B shall be that of which temperature column, and it shall not exceed the 60°C ampacity when installed in thermal insulation?

• AThe 90°C column of Table 310.16 with no further limit
• BThe 60°C column of Table 310.16
• CThe 75°C column only
• DThe 30°C ambient column of Table 310.17

A 120-volt, single-phase branch circuit supplies 16 amperes over 180 feet of 10 AWG copper. Use K = 12.9 and 10,380 CM. What is the voltage drop?

• A3.6 V
• B12.4 V
• C7.2 V
• D5.1 V

A raceway is installed outdoors in a wet location. Which conductor type is acceptable without relying on a dual-rated marking?

• ATHHN only, with no wet-location rating
• BTW only inside a raintight trough
• CUnlisted fixture wire
• DTHWN or THWN-2

When determining the number of current-carrying conductors for ampacity adjustment, a neutral conductor shall be counted in which situation?

• AWhen it carries a major portion of the load from nonlinear loads, or when it carries curr…
• BNever; neutrals are never counted
• CAlways, including a balanced linear 4-wire wye feeder
• DOnly when it is bare

NEC 2020 310.10(G) generally requires paralleled conductors to be at least which size?

• A2 AWG
• B1/0 AWG
• C4 AWG
• D250 kcmil

Type SE cable is used as an interior feeder installed in thermal insulation. Per NEC 2020 338.10(B)(4), the ampacity shall be determined in accordance with which rule?

• ATable 310.17 free-air ampacity with no adjustment
• BArticle 400 flexible-cord ampacity
• CThe 334.80 NM-cable ampacity rule, so the final ampacity shall not exceed the 60°C rating
• DThe 90°C column as the final ampacity in all cases

Which identification is required by the NEC 2020 for a grounded conductor, an equipment grounding conductor, and an ungrounded conductor in a 120/240-volt system?

• AGreen for the grounded conductor and white for the EGC
• BBlack for all conductors if they are tagged at each end
• COrange for the grounded conductor on a high-leg system
• DWhite or gray for the grounded conductor; green, green with yellow stripe, or bare for th…

Unless the equipment is listed and marked otherwise, NEC 2020 110.14(C)(1) generally requires conductors 14 AWG through 1 AWG, or circuits 100 amperes or less, to have their ampacity selected from which temperature column?

• AThe 60°C column
• BThe 90°C column
• CThe 105°C column
• DThe 30°C free-air column

A metal device box contains internal cable clamps and one single-gang device. Three 12/2 NM cables with grounds enter the box. NEC 2020 Table 314.16(B) assigns 2.25 cubic inches to each 12 AWG volume allowance. What is the minimum required box volume?

• A13.50 in³
• B22.50 in³
• C18.00 in³
• D20.25 in³

A box contains six 14 AWG insulated conductors, all associated equipment grounding conductors, internal cable clamps, and one device. Table 314.16(B) assigns 2.00 cubic inches to 14 AWG. What minimum volume is required?

• A12.00 in³
• B16.00 in³
• C20.00 in³
• D18.00 in³

Unless listed for other support, NEC 2020 358.30(A) requires EMT to be securely fastened within which distance of each outlet box and at what maximum interval?

• AWithin 12 inches of each box and at intervals not exceeding 4.5 feet
• BWithin 8 feet of each box and at intervals not exceeding 15 feet
• CNo intermediate support is required if the run is less than 20 feet
• DWithin 3 feet of each box and at intervals not exceeding 10 feet

NEC 2020 Table 352.30 lists PVC support intervals of 3 feet for 1/2-inch through 1-inch conduit and 5 feet for 1-1/4-inch through 2-inch conduit. A 3/4-inch Schedule 40 PVC run must be supported at what maximum interval, and it must also be fastened within 3 feet of each box?

• A3 feet
• B5 feet
• C10 feet
• D8 feet