NEC Questions Practice Test-14
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Question 1 of 10
1. Question
1 pointsIf the conduit is placed in hazardous locations , it must be made ……………….. to prevent sparking when fault current flow through it.
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Refer : NEC 500.8(E)
Conduit should be made wrentch tight to avoid sparking
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Question 2 of 10
2. Question
1 pointsWhat are the maximum allowable service dis connectors consist for each service?
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Refer: NEC 230.71 (A)
Not more than six switches or six circuit breakers should not be there on each service disconnection.
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Question 3 of 10
3. Question
1 pointsWhat is the smallest rating plug fuse that is used for residential 120 volts branch circuit?
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Refer : NEC 240.6(A)
The standard plug fuse ratings are 15,20,25 ad 30.
15 amperes is the smallest fuse rating
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Question 4 of 10
4. Question
1 pointsWhat is the voltage drop of two 10 AWG THWN conductors that supply 16 amperes 115 volts load located 50 feet from the source?
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Refer : NEC Chapter 9 Table 9
10 AWG THWN resistance = 1.2 volts / 1000 feet
two cables of 50 feet , so resistance = (1.2 / 1000) * 100 = 0.12 volts
current I = 16 amperes
voltage drop = I * R = 16 * 0.12 = 1.92 volts
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Question 5 of 10
5. Question
1 pointsWhat is the minimum volt ampere rating of a 110,000 square foot school?
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Refer : NEC Table 220.12
The minimum volt ampere for a school = 3 VA / square foot
Total volt ampere = 110,000 * 3 = 330,000 VA = 330 KVA
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Question 6 of 10
6. Question
1 pointsA disconnecting means should be visibly located from a motor not more than ………….. distance.
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Refer: NEC article 100
They must nor be more than 50 feet visibly from the motor compartment.
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Question 7 of 10
7. Question
1 pointsA 4800 watts electric motor is connected to 240 volts single phase supply, 2 wire circuit. what is the minimum size THW conductor that is required to supply the load?
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Current = 4800 / 240 = 20 amperes
Refer: NEC 424.3 (B)
motors should be treated as continuous load
Refer: NEC 210.20(A)
Over current devices should be 125% of continuous load
over current device rating = 1.25 * 20 = 25 amperes
Refer: NEC Table 310.15(B)(16)
NO 10 AWG with 30 amperes allowable ampacity is the suitable conductor
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Question 8 of 10
8. Question
1 pointsWhat is the minimum allowable 3 wire service entrance conductor rating for a single family dwelling unit?
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Incorrect
Refer : NEC 230.42 (B)
un- grounded conductors for a specific installations not to be less than service disconnecting means
Refer : NEC 230.79(C)
Disconnecting means for a single family dwelling unit must not be less than 100 amperes
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Question 9 of 10
9. Question
1 pointsAn electric heater with a resistance of 18 ohms draws a current of 7 amperes. what is the minimum wattage of electric heater?
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Incorrect
Power P = I2 * R
P = (7 * 7 ) * 18 = 882 watts.
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Question 10 of 10
10. Question
1 pointswhat is the maximum over current device rating that is allowed to placed to protect panel board instrumentation circuit?
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Incorrect
Refer : NEC 408.52
The maximum allowable over current device rating for panel board instrumentation circuit is 15 amperes.