NEC Code Questions Practice Test-18
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Question 1 of 10
1. Question
1 pointsAn enclosed channel which holds wires,cables or bus-bars is called as:
Correct
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Refer : NEC 100 Definitions
A raceway is an enclosed channel which holds cables or bus bars.
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Question 2 of 10
2. Question
1 pointsAn ohmmeter connected across 240 electric heater shows the reading of 20 ohms. What is the current flow in the electric heater?
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Incorrect
Current Flow = Voltage / Resistance
I = 240 / 20 = 12 amperes
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Question 3 of 10
3. Question
1 pointsA residence has an area of 60 feet by 30 feet. Which of the following is the minimum allowable 120 volts , 20 amperes branch circuits required for general lightening?
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Incorrect
Total area of residence = 60 * 30 = 1800 square feet.
Minimum General lightening load for a residence is 3 VA/ square feet.
Total general lightening load = 1800 * 3 = 5400 VA.
Total current flows in 120 volt circuit = 5400 / 120 = 45 amperes
Minimum number 20 ampere branch circuits = 45 / 20 = 2.25 ( next higher value is 3)
So total 3 , 20 ampere lightening branch circuits are required.
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Question 4 of 10
4. Question
1 pointsA 4 AWG THHN conductor is used to connect a 480 Volts, 3 phase 35 KVA transformer to panel board. what is the maximum length of conductor that can be used in which the voltage drop does not cross 3%?
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Incorrect
Voltage Drop VD = 1.732 * K * I * D/CM
D = (VD * CM) / (1.732 * K * I )
K = 12.9 (Copper)
I = 35000 / ( 1.732 * 480) = 42 A
CM = 41740 ( Chapter 9 Table 8)
D = ( 14.4 * 41740 ) / ( 1.732 * 12.9 * 42 )
= 640 feet.
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Question 5 of 10
5. Question
1 pointsThe over load protection must be provided for the motor if it is rated more than …………… Hp.
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Incorrect
Refer : NEC 430.32 (A)
If motor rated more than 1 Hp must be protected with an approved overload protection.
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Question 6 of 10
6. Question
1 pointsWhat is the maximum continuous load that can be connected to 240 volts 30 amperes branch circuit?
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Incorrect
Refer : NEC 210.20
The continuous load should have conductors rated 125% above the connected load.
The maximum permitted load = 30 / 1.25 = 24 amperes
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Question 7 of 10
7. Question
1 pointsA incandescent-lamp must not be equipped with medium base if rated more than …………… watts.
Correct
Incorrect
Refer: 410.103
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Question 8 of 10
8. Question
1 pointsIn a 14 feet residential hallway, how many minimum number of receptacles are required?
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Incorrect
Refer: NEC 210.52 ( H)
At least one receptacle is required in 10 feet or more in length hallways.
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Question 9 of 10
9. Question
1 pointsFor an electric motor rated not more than …………… horsepower, the branch circuit can server as disconnecting means.
Correct
Incorrect
Refer : 422.31 (A)
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Question 10 of 10
10. Question
1 pointsWhat is the minimum volt ampere rating of a 180,000 square foot school?
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Incorrect
Refer : NEC Table 220.12
The minimum volt-ampere for a school = 3 VA / square foot
Total volt-ampere = 180,000 * 3 = 540 KVA