Test Your Security Installation Formulas Knowledge
Stick to the Formula
All Answers relate to NFPA 70, 2017 Edition
1. The “PIE” formula wheel designations relate to what?
A. P=Power, I=Input, E=Equation
B. P=Potential, I=Resistance, E=Wattage
C. P=Power, I=Current, E=Voltage
D. P=Percentage, I=Volume, E=Resistance
Feedback: P=Power, I=Current, E=Voltage
2. Determine the power loss in watts for two conductors that carry 10A and have a voltage drop of 4.5V.
A. 0.45
B. 450
C. 45
D. 4.5
Feedback: 45
3. Which of the following formulas represent Ohm’s Law? (Choose all that apply.)
A. E=IxR
B. P-IxE
C. I=E/R
D. R=E/I
Feedback: A, C & D
4. What is the volume, in cubic inches, of a junction box that measures 4x4x1½-in.?
A. 16
B. 24
C. 4
D. 17.5
Feedback: 24
5. ______ states that the sum of currents flowing through each resistor of a series circuit is the same.
A. Kirchoff’s Voltage Law
B. Kirchoff’s Current Law
C. Kirchoff’s Power Law
D. Kirchoff’s Resistance Law
Feedback: Kirchoff’s Current Law
6. See SDM print edition, August 2018, p. 84.
7. A lamp has a resistance of 150 Ohms. It is powered by 120V. What is the current in the circuit?
A. 0.8A
B. 180A
C. 1,800A
D. 8A
Feedback: 0.8
8. The resistance of two 22AWG conductors 75 ft. long is 0.4 Ohms, and the current through the circuit is 15A. What is the power loss in watts of the conductors?
A. 120
B. 102.4
C. 140.2
D. 12.0
Feedback: 102.4/div>
9. What is the reciprocal of 75 percent?
A. 0.75
B. 13.3
C. 1.33
D. 7.5
Feedback: 1.33
10. Which of the following is not a method of calculating resistance of a parallel circuit?
A. Equal Resistance Method
B. Product-Over-Sum Method
C. Reciprocal Method
D. Consumed Power Method
Feedback: Consumed Power Method
11. The total resistance of a circuit with three 15 Ohm resistors in parallel is ______.
A.45
B. 5
C. 4.5
D. 0.5
Feedback: 5
12. According to Table 314.16(A) of the NEC, what is the maximum number of 16AWG conductors permitted to be installed in a 4x4x21⁄8-in. square metal box?
A. 20
B. 17
C. 15
D. 13
Feedback: 17
13. Based on the same table in question 12, would the maximum number of conductors permitted be different if the box was of the same dimension but it was round/octagonal?
A. Yes
B. No
Feedback: Yes
14. Based on the same table in question 12, what is the minimum volume specified for a round/octagonal 4 in. x 1½-in. metal box?
A. 15.5
B. 18
C. 21.0
D. 12.5
Feedback: 15.5
15. When calculating box fill, according to Table 314.16(A), you are required to take into consideration the size and shape of switches, receptacles, cable clamps or equipment grounding conductors.
A. True
B. False
Feedback: False
Post-Quiz Extra: Can you identify?
The NEC provides guidance for conduit fill. Looking at this diagram, determine the proper maximum percentage fill permitted by the NEC. Where in the NEC would you find the answer?
Click here to see the answer.
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