CSLB C-10 Electrical Contractor License Exam (C10 Planning & Estimating) | Complete Exam Study Guide with Actual Exam Questions, Verified Correct Answers and Detailed Rationales | Latest Update 2026/2027 – Already Graded A+

CSLB C-10 Electrical Contractor License Exam (C10
Planning & Estimating) | Complete Exam Study Guide with
Actual Exam Questions, Verified Correct Answers and
Detailed Rationales | Latest Update 2026/2027 – Already
Graded A+

Question 1
What is the typical operating frequency of alternating current?
A. 60 Hz
B. 120 Hz
C. 40 Hz
D. 50 Hz
Answer: A
Rationale: The typical operating frequency of alternating current in North
America is 60 Hz. This is the standard frequency used by utility companies for
power distribution.


Question 2
Which of the following connects a ground wire to the grounding rod?
A. Circuit breaker
B. Grounding rod clamp
C. Copper conduit
D. Electrical tape
Answer: B
Rationale: A grounding rod clamp is used to connect the ground wire (grounding
electrode conductor) to the grounding rod. This ensures a secure electrical
connection between the grounding system and the earth.



pg. 1

,Question 3
If you have to install a ground rod in rocky soil what is acceptable per NEC
250.53(G)?
A. Cut the ground rod in half and drive 4' deep
B. Lay ground rod horizontal 12" deep
C. Lay ground rod horizontal 30" deep
D. Drive ground rod as far as you can then cut excess off
Answer: C
Rationale: NEC 250.53(G) permits grounding electrodes to be buried horizontally
in a trench at least 30 inches deep when rocky soil prevents vertical installation.
This ensures the electrode maintains adequate contact with the earth.


Question 4
Refer to the 1st floor Electric blueprint. How many GFCI receptacles are found on
this floor level?
A. 5
B. 120°
C. 1
D. 11
Answer: A
Rationale: Based on the blueprint, there are 5 GFCI receptacles located on the first
floor of the residence.


Question 5
Refer to the diagram below. What is the maximum current rating of the inverter?
A. 240
B. 48
C. 480
D. 5200



pg. 2

,Answer: A
Rationale: The maximum current rating of the inverter is 240 as shown in the
diagram.


Question 6
Refer to the Electric blueprint. How many receptacles are needed for this whole
house? Note: Include all receptacle types even those that are not depicted but
belong.
A. 40
B. 10
C. 14
D. 11
Answer: A
Rationale: The blueprint shows a total of 40 receptacles required for the entire
house, including all types such as duplex, GFCI, and AFCI receptacles.


Question 7
If you are connecting a 12-V battery set, what PV system design would you
consider for your modules?
A. 9V modules
B. 24V modules
C. 12V modules
D. 30V modules
Answer: C
Rationale: When using a 12-volt battery set, you should use 12-volt modules to
match the system voltage. This ensures proper charging and system compatibility.


Question 8
Refer to the 1st floor Electric blueprint. How many single-pole switches are
needed?

pg. 3

, A. 24
B. 3
C. 12
D. 40
Answer: C
Rationale: The blueprint shows 12 single-pole switches are required on the first
floor.


Question 9
How is resistance measured?
A. Amps
B. Ohms
C. Current
D. Volts
Answer: B
Rationale: Resistance is measured in ohms. The unit of measurement is named
after Georg Simon Ohm, who formulated Ohm's Law.


Question 10
Refer to the 1st floor Electric blueprint. How many three-way switches are needed?
A. 12
B. 1
C. 11
D. 16
Answer: C
Rationale: The blueprint shows 11 three-way switches are needed on the first
floor.


Question 11
How many kWh will be consumed by a 500W lightbulb running for 3 hours?
pg. 4