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These 10 free CA-C10 questions are organized by exam domain, so you can see how each part of the California C-10 Electrical Contractor License Exam blueprint is tested. Reveal the answer and explanation under each question.
An estimator is selecting a replacement 100-A, 3-pole breaker for a 480-V panel where calculated available fault current is 18 kA. The physically compatible breaker under consideration is rated 100 A, 480 V, and 10 kA interrupting. What should be specified?
Correct answer: A - A listed compatible breaker, or a fully listed series-rated combination, rated for at least 18 kA at 480 V
A 2,000-ft² dwelling has the required two small-appliance circuits, one laundry circuit, and one household dryer rated 4,800 VA. Use 3 VA/ft²; include 1,500 VA for each required small-appliance and laundry circuit; apply 100% to the first 3,000 VA and 35% to the remainder of the general load; and use 5,000 VA or the dryer nameplate, whichever is larger. What load should be carried before adding range, HVAC, or other appliance loads?
Correct answer: C - 10,625 VA
A standby generator uses a 4-pole transfer switch that opens the neutral when transferring between utility and generator. For grounding and bonding design, how should the generator generally be classified?
Correct answer: A - As a separately derived system, with the system bond at the generator or first disconnect as permitted
A new 120-V, 20-A branch circuit supplies receptacles along the countertop of a dwelling kitchen. The required protection for those receptacle outlets is:
Correct answer: C - Both GFCI and AFCI protection because the devices address different hazards
A 277/480-V panelboard with exposed live parts on the front will face a bare concrete wall. The planned clear depth from the panel face to the wall is 39 in. How should the layout be revised?
Correct answer: D - Increase the clear depth to at least 42 in
A continuous-duty three-phase motor has a code-table full-load current of 28 A and a nameplate current of 26 A. Its service factor is 1.15. For an ordinary installation, which pair gives the minimum branch-circuit conductor ampacity and the initial maximum overload setting?
Correct answer: A - 35 A conductor ampacity and 32.5 A overload setting
During troubleshooting of a 120/240-V, single-phase service, a technician measures 241 V from L1 to L2. With several 120-V loads operating, L1-to-neutral fluctuates between 158 and 170 V while L2-to-neutral fluctuates between 83 and 71 V. The most likely fault is:
Correct answer: B - An open or high-resistance service neutral
At midday under uniform irradiance, four parallel photovoltaic strings have nearly identical open-circuit voltages. When connected for operation, one string delivers 0 A while the other three deliver normal current. This combination most strongly indicates:
Correct answer: B - An open connector, open disconnect, or blown string fuse
An energized diagnostic task is justified. The arc-flash study gives incident energy of 9.6 cal/cm² at the working distance, and the incident-energy method rather than a PPE-category table is being used. Which statement about the required arc rating is correct?
Correct answer: D - The arc-rated clothing/PPE system must be rated at least 9.6 cal/cm²
On a construction site, temporary 120-V, single-phase, 20-A receptacles are supplied by a properly grounded temporary panel. Which compliance method is permitted for personnel ground-fault protection?
Correct answer: C - GFCI protection or an implemented assured equipment-grounding conductor program
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