Page 1 of 169
CSLB C10 TEST EXAM ALL 300 RANDOMIZED
PRACTICE QUESTIONS WITH ANSWERS &
RATIONALES LATEST VERSION THIS YEAR
1. What is the minimum working clearance required in front of an electrical panel rated under 600 volts?
A) 24 inches
B) 30 inches
C) 36 inches
D) 42 inches
Answer: C NEC 110.26(A)(1) requires a minimum working clearance of 36 inches in front of electrical
equipment operating at 600 volts or less to provide safe access for maintenance and operation.
2. Voltage drop in a wire is a function of which of the following factors?
A) Wire gauge only
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B) Length of wire only
C) Wire gauge, length of wire, and current flow
D) Ambient temperature only
Answer: C Voltage drop is determined by wire gauge (resistance per foot), total length of the conductor,
and the amount of current flowing through it.
3. A 12-volt DC, 13-watt fluorescent light is controlled by a photocell. The average daily on-time is 12
hours per day. How many watt-hours are consumed by the light on an average day?
A) 120 Wh
B) 144 Wh
C) 156 Wh
D) 168 Wh
Answer: C Watt-hours = Watts × Hours = 13 × 12 = 156 Wh.
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4. According to the NEC, what is the maximum distance a receptacle outlet can be placed from any point
along a wall in a dwelling?
A) 4 feet
B) 6 feet
C) 12 feet
D) 20 feet
Answer: C NEC 210.52(A)(1) requires that no point along a wall in a dwelling be more than 6 feet from a
receptacle; therefore, receptacles can be spaced up to 12 feet apart.
5. What is the minimum wire size allowed for a 20-amp residential branch circuit?
A) 14 AWG
B) 12 AWG
C) 10 AWG
D) 8 AWG
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Answer: B NEC Table 310.16 requires #12 AWG copper for a 20-amp circuit (60°C column).
6. When installing a grounding electrode conductor, which of the following materials is acceptable?
A) Aluminum wire
B) Copper wire
C) Steel wire without coating
D) Plastic-coated wire
Answer: B Copper is the standard material for grounding electrode conductors. Aluminum is not
permitted for this application per NEC 250.62.
7. What is the maximum number of conductors allowed in a conduit before derating is required?
A) 3
B) 4
CSLB C10 TEST EXAM ALL 300 RANDOMIZED
PRACTICE QUESTIONS WITH ANSWERS &
RATIONALES LATEST VERSION THIS YEAR
1. What is the minimum working clearance required in front of an electrical panel rated under 600 volts?
A) 24 inches
B) 30 inches
C) 36 inches
D) 42 inches
Answer: C NEC 110.26(A)(1) requires a minimum working clearance of 36 inches in front of electrical
equipment operating at 600 volts or less to provide safe access for maintenance and operation.
2. Voltage drop in a wire is a function of which of the following factors?
A) Wire gauge only
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B) Length of wire only
C) Wire gauge, length of wire, and current flow
D) Ambient temperature only
Answer: C Voltage drop is determined by wire gauge (resistance per foot), total length of the conductor,
and the amount of current flowing through it.
3. A 12-volt DC, 13-watt fluorescent light is controlled by a photocell. The average daily on-time is 12
hours per day. How many watt-hours are consumed by the light on an average day?
A) 120 Wh
B) 144 Wh
C) 156 Wh
D) 168 Wh
Answer: C Watt-hours = Watts × Hours = 13 × 12 = 156 Wh.
, Page 3 of 169
4. According to the NEC, what is the maximum distance a receptacle outlet can be placed from any point
along a wall in a dwelling?
A) 4 feet
B) 6 feet
C) 12 feet
D) 20 feet
Answer: C NEC 210.52(A)(1) requires that no point along a wall in a dwelling be more than 6 feet from a
receptacle; therefore, receptacles can be spaced up to 12 feet apart.
5. What is the minimum wire size allowed for a 20-amp residential branch circuit?
A) 14 AWG
B) 12 AWG
C) 10 AWG
D) 8 AWG
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Answer: B NEC Table 310.16 requires #12 AWG copper for a 20-amp circuit (60°C column).
6. When installing a grounding electrode conductor, which of the following materials is acceptable?
A) Aluminum wire
B) Copper wire
C) Steel wire without coating
D) Plastic-coated wire
Answer: B Copper is the standard material for grounding electrode conductors. Aluminum is not
permitted for this application per NEC 250.62.
7. What is the maximum number of conductors allowed in a conduit before derating is required?
A) 3
B) 4
