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NEC CODE NEC 2023

Voltage Drop Calculations (NEC Code Questions)

Free online practice test on Conductor Voltage Drop calculations.

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Frequently Asked Questions

Yes — free, no signup required. Each question links to the relevant NEC article so you can study the code directly.

The National Electrical Code (NFPA 70) is the benchmark standard for safe electrical installation in the US. It is updated every 3 years by the NFPA.

Study the edition adopted by your state. As of 2025, most states use the 2020 or 2023 NEC. These tests are written to the 2023 edition.

The most tested articles are 100 (Definitions), 200–250 (Wiring & Grounding), 300–314 (Wiring Methods), 400–411 (Conductors), 430 (Motors), and 700–701 (Emergency Systems).

How to Use This Practice Test

This Voltage Drop Calculations (NEC Code Questions) has 10 questions with detailed answers and NEC references. Take the full test, review every wrong answer, and look up the NEC article it references before moving on.

Tip: Use the NEC index (back of the book) — find answers by keyword, not by article number.

Topics covered: NEC articles 100, 210, 220, 240, 250, 300, 310, 430, and special occupancies.
Passing score: Aim for 80%+ on NEC code tests before exam day.
Questions: 10 multiple-choice, one correct answer each

10

Questions

15 min

Time

70%

Pass

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Voltage Drop Calculations (NEC Code Questions) — Question List

Question 1: What is the minimum NEC recommended voltage for a 230 volt load connected to 240 v source?

230 V
228 V
232 V
225 V

Question 2: If a 115 volt load is connected to 120 V source. What is minimum voltage that is supplied to the load as recommended by NEC?

114 V.
115 V
120 V
117 V

Question 3: What is the voltage drop of two 10 AWH THHN conductors that supply 16 A, 115 V load located 50 ft from the source?

1.92 V
0,96
2.4 V
1.8 V

Question 4: Two 12 AWG THHN conductors are placed to connect 8A, 120 V load to the source which is 100 ft distance. What is maximum voltage drop in conductor?

3.2 Volts
6.4 Volts
1.92 Volts
2.4 Volts

Question 5: A 3 phase 18 KVA, 208 volts load is connected to panel board with 100 ft length of 2AWG THHN copper conductor. What is the approximate voltage drop in the conductor?

1.68 volts
3.2 Volts
2.4 volts
3.8 volts

NEC Reference: NEC 12.9

Question 6: A 12 KVA , 3 phase 480 Volts load should be connected to panel board with a distance of 220 ft. What size conductor is required to prevent the voltage drop from exceeding 3 %?

12 AWG
10 AWG
8 AWG
14 AWG

NEC Reference: NEC 12.9

Question 7: A 4 AWG THHN is used to connect a 480 V 3 phase 35 kVA transformer to panel board. what is the maximum length of conductor that can be used in which the voltage drop doesn't cross 3% ?

640 ft
320 ft
720 ft
540 ft

NEC Reference: NEC 14.4

Question 8: What is the maximum voltage drop that is recommended by NEC for both branch and feeder conductors?

3 %
4 %
5 %
6 %

Question 9: What is 3 phase load that can be connected to a 220 ft, 8 THHN, 480 V conductor with out exceeding the NEC recommended voltage drop?

40 KVA
42 KVA
48 KVA
53 KVA

NEC Reference: NEC 12.9

Question 10: What is maximum voltage drop in percentage recommended by NEC for branch circuit conductors?

3 %
5 %
2 %
4 %

Key NEC References for This Test

Article	What It Covers
Ch. 1–4	General rules — apply to all installations
Ch. 5–7	Special rules — override Ch. 1–4 where they conflict
Ch. 8	Communications — completely independent of Ch. 1–7
Ch. 9	Tables — referenced by articles, not standalone enforceable rules
Art. 210.12	AFCI — major expansion in NEC 2026
Art. 230.67	Surge protection at service equipment — new NEC 2026

Study Tip: Learn the NEC index — use keywords, not article numbers. Practice finding 5 different topics in under 2 minutes each.

EXAM CARD NEC CODE

Questions10

Time limit15 min

Pass score70%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

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Source: NEC 2026 (NFPA 70)