ILLINOIS JOURNEYMAN ELECTRICIAN | NEC EXAM | 200
Practice Questions , Answers with Rationales
**1. What is the minimum working space depth required in front of a 480V panelboard?**
A) 2 feet
B) 3 feet
C) **3.5 feet (correct answer)**
D) 4 feet
Rationale:** Per NEC 110.26(A)(1), the minimum depth of working space for 151-600V
systems is 3.5 feet (42 inches) for Condition 1 (exposed live parts on one side).
**2. What is the maximum allowable voltage drop recommended by the NEC for feeders?**
A) 2%
B) **3% (correct answer)**
C) 5%
D) 10%
**Rationale:** While not enforceable as a code requirement, NEC 215.2(A)(1) Informational
Note No. 4 recommends a maximum voltage drop of 3% for feeders and 5% overall for feeders
and branch circuits combined.
**3. What type of conduit is permitted for use in cinder fill?**
A) EMT
B) **Rigid Metal Conduit (correct answer)**
C) PVC Schedule 40
D) FMC
**Rationale:** NEC 300.5(D) prohibits EMT, PVC, and FMC in cinder fill unless protected by 2
inches of non-cinder concrete. RMC is permitted as it provides superior corrosion resistance.
,**4. What is the minimum size THHN conductor permitted for a 20-ampere branch circuit?**
A) 14 AWG
B) **12 AWG (correct answer)**
C) 10 AWG
D) 8 AWG
**Rationale:** NEC 210.19(A)(4) requires branch circuit conductors to have an ampacity not
less than the branch circuit rating. Table 310.16 shows 12 AWG THHN at 60°C is rated for 20
amperes.
---
**5. At what height must a disconnecting means be mounted for a residential air conditioning
unit?**
A) Not over 4 feet
B) Not over 5 feet
C) **Not over 6 feet 7 inches (correct answer)**
D) Not over 7 feet
**Rationale:** NEC 440.14 requires the disconnecting means to be readily accessible and
located within sight from the equipment. It must not be located more than 6 feet 7 inches
above the floor or working platform.
---
**6. What is the ampacity of a 500 kcmil THHN copper conductor in a dry location at 75°C?**
A) 350 amperes
B) 380 amperes
C) **380 amperes (correct answer)**
D) 430 amperes
,**Rationale:** NEC Table 310.16 lists 500 kcmil THHN copper at 75°C with an ampacity of 380
amperes. The 90°C column (430A) can only be used for derating purposes.
---
**7. What is the maximum number of overcurrent devices permitted in a lighting and appliance
panelboard?**
A) 24
B) 36
C) **42 (correct answer)**
D) 48
**Rationale:** NEC 408.54 limits lighting and appliance branch-circuit panelboards to not more
than 42 overcurrent devices (excluding the main). This was formerly 42 and has been
maintained.
---
**8. What is the minimum burial depth for rigid metal conduit under a commercial parking lot?
**
A) 12 inches
B) 18 inches
C) **24 inches (correct answer)**
D) 30 inches
**Rationale:** NEC Table 300.5 requires a minimum cover of 24 inches for RMC under areas
subject to vehicular traffic. Residential driveways require 18 inches, but commercial parking lots
require 24 inches.
---
, **9. What is the maximum continuous load permitted on a 20-ampere branch circuit?**
A) 16 amperes
B) **16 amperes (correct answer)**
C) 18 amperes
D) 20 amperes
**Rationale:** NEC 210.20(A) requires branch circuit conductors and overcurrent devices to be
sized at 125% of continuous loads. Therefore, 20A ÷ 1.25 = 16A maximum continuous load.
---
**10. What color is required for the grounded conductor (neutral) in a 120/208V system?**
A) Green
B) White or gray
C) **White or gray (correct answer)**
D) Yellow
**Rationale:** NEC 200.6 requires the grounded conductor to be identified by white or gray
color. Green is reserved for equipment grounding conductors per 250.119.
---
**11. What is the minimum size grounding electrode conductor for a service with 3/0 AWG
ungrounded conductors?**
A) 4 AWG
B) **4 AWG (correct answer)**
C) 2 AWG
D) 1/0 AWG
Practice Questions , Answers with Rationales
**1. What is the minimum working space depth required in front of a 480V panelboard?**
A) 2 feet
B) 3 feet
C) **3.5 feet (correct answer)**
D) 4 feet
Rationale:** Per NEC 110.26(A)(1), the minimum depth of working space for 151-600V
systems is 3.5 feet (42 inches) for Condition 1 (exposed live parts on one side).
**2. What is the maximum allowable voltage drop recommended by the NEC for feeders?**
A) 2%
B) **3% (correct answer)**
C) 5%
D) 10%
**Rationale:** While not enforceable as a code requirement, NEC 215.2(A)(1) Informational
Note No. 4 recommends a maximum voltage drop of 3% for feeders and 5% overall for feeders
and branch circuits combined.
**3. What type of conduit is permitted for use in cinder fill?**
A) EMT
B) **Rigid Metal Conduit (correct answer)**
C) PVC Schedule 40
D) FMC
**Rationale:** NEC 300.5(D) prohibits EMT, PVC, and FMC in cinder fill unless protected by 2
inches of non-cinder concrete. RMC is permitted as it provides superior corrosion resistance.
,**4. What is the minimum size THHN conductor permitted for a 20-ampere branch circuit?**
A) 14 AWG
B) **12 AWG (correct answer)**
C) 10 AWG
D) 8 AWG
**Rationale:** NEC 210.19(A)(4) requires branch circuit conductors to have an ampacity not
less than the branch circuit rating. Table 310.16 shows 12 AWG THHN at 60°C is rated for 20
amperes.
---
**5. At what height must a disconnecting means be mounted for a residential air conditioning
unit?**
A) Not over 4 feet
B) Not over 5 feet
C) **Not over 6 feet 7 inches (correct answer)**
D) Not over 7 feet
**Rationale:** NEC 440.14 requires the disconnecting means to be readily accessible and
located within sight from the equipment. It must not be located more than 6 feet 7 inches
above the floor or working platform.
---
**6. What is the ampacity of a 500 kcmil THHN copper conductor in a dry location at 75°C?**
A) 350 amperes
B) 380 amperes
C) **380 amperes (correct answer)**
D) 430 amperes
,**Rationale:** NEC Table 310.16 lists 500 kcmil THHN copper at 75°C with an ampacity of 380
amperes. The 90°C column (430A) can only be used for derating purposes.
---
**7. What is the maximum number of overcurrent devices permitted in a lighting and appliance
panelboard?**
A) 24
B) 36
C) **42 (correct answer)**
D) 48
**Rationale:** NEC 408.54 limits lighting and appliance branch-circuit panelboards to not more
than 42 overcurrent devices (excluding the main). This was formerly 42 and has been
maintained.
---
**8. What is the minimum burial depth for rigid metal conduit under a commercial parking lot?
**
A) 12 inches
B) 18 inches
C) **24 inches (correct answer)**
D) 30 inches
**Rationale:** NEC Table 300.5 requires a minimum cover of 24 inches for RMC under areas
subject to vehicular traffic. Residential driveways require 18 inches, but commercial parking lots
require 24 inches.
---
, **9. What is the maximum continuous load permitted on a 20-ampere branch circuit?**
A) 16 amperes
B) **16 amperes (correct answer)**
C) 18 amperes
D) 20 amperes
**Rationale:** NEC 210.20(A) requires branch circuit conductors and overcurrent devices to be
sized at 125% of continuous loads. Therefore, 20A ÷ 1.25 = 16A maximum continuous load.
---
**10. What color is required for the grounded conductor (neutral) in a 120/208V system?**
A) Green
B) White or gray
C) **White or gray (correct answer)**
D) Yellow
**Rationale:** NEC 200.6 requires the grounded conductor to be identified by white or gray
color. Green is reserved for equipment grounding conductors per 250.119.
---
**11. What is the minimum size grounding electrode conductor for a service with 3/0 AWG
ungrounded conductors?**
A) 4 AWG
B) **4 AWG (correct answer)**
C) 2 AWG
D) 1/0 AWG
