CSLB-Electrical Contractor Exam (C-10) Law & Business + Trade
Questions And Answers| Exam Prep |All Questions And
Answers 2026/2027 | Verified Answers Plus Rationales |
Graded Q&A Comprehensive Study Guide | Verified Latest
2027
1. According to California Contractors License Law, what is the maximum initial down
payment a licensed electrical contractor can legally require for a residential home
improvement contract?
A. $1,000 or 10% of the contract price, whichever is less
B. $1,000 or 10% of the contract price, whichever is greater
C. 25% of the total contract price
D. $500 or 5% of the contract price, whichever is less
Rationale: Under California Business and Professions Code Section 7159, the down payment
for any residential home improvement contract cannot exceed $1,000 or 10% of the total
contract price, whichever amount is less. Requiring more than this legal threshold is a
misdemeanor offense subject to disciplinary action by the CSLB.
2. A C-10 contractor is performing a commercial tenant improvement project. What is the
minimum depth required for underground direct-burial UF cable operating at 120V and
protected by a 20A GFCI circuit breaker in a location not subject to vehicular traffic?
A. 24 inches
B. 18 inches
C. 12 inches
D. 6 inches
Rationale: According to NEC Table 300.5, Column 4, residential or commercial 120V branch
circuits rated 20A or less and protected by a GFCI before entering the ground require a
minimum burial depth of only 12 inches when located in areas not subject to vehicular traffic.
Standard non-GFCI direct-burial cables require 24 inches.
3. An electrical contractor hires a new journey-level electrician. Within how many days
must the contractor report the hiring to their Workers' Compensation insurance carrier to
maintain complete regulatory compliance?
,A. 10 days
B. 30 days
C. Reporting guidelines are governed by policy terms, but all wages must be reported on the
periodic payroll audit
D. 60 days
Rationale: While new employees must be registered with the California Employment
Development Department (EDD) within 20 days via Form DE 34, Workers' Compensation
policy compliance requires accurate reporting of all payroll during mandatory periodic policy
audits, rather than single-employee initial notifications unless specifically dictated by insurer
policy terms.
4. When calculating total service load for a commercial building, what multiplier must be
applied to continuous loads under the provisions of NEC Article 210?
A. 100%
B. 115%
C. 125%
D. 140%
Rationale: NEC 210.20(A) mandates that branch circuit overcurrent protective devices and
conductors feeding continuous loads (loads operating continuously for 3 hours or more) must
be sized at not less than 125% of the continuous load plus 100% of the non-continuous load.
5. What is the maximum distance allowed between supporting straps for a 1-inch rigid
metal conduit (RMC) run along a flat masonry wall?
A. 6 feet
B. 8 feet
C. 10 feet
D. 12 feet
Rationale: Pursuant to NEC 344.30(A), Rigid Metal Conduit (RMC) must be supported at
intervals not exceeding 10 feet. Furthermore, it must be securely fastened within 3 feet of
each conduit termination, box, or enclosure.
,6. Under California mechanics' lien law, within how many days must a subcontractor file a
Preliminary 20-Day Notice after starting work to preserve their full mechanics' lien rights?
A. 10 days
B. 20 days
C. 30 days
D. 60 days
Rationale: California Civil Code requires sub-tier contractors to serve a Preliminary 20-Day
Notice within 20 days of first furnishing labor, materials, or equipment to a jobsite. Serving it
later limits lien rights strictly to work provided during the 20 days prior to service and
thereafter.
7. In a standard 3-phase, 4-wire delta system (high-leg delta), what is the color
identification required by the NEC for the conductor with the higher voltage to ground?
A. Red
B. Orange
C. Yellow
D. Blue
Rationale: NEC 110.15 specifies that on a 4-wire, delta-connected system where the midpoint
of one phase winding is grounded, the conductor having the higher phase voltage to ground
(the "high-leg", typically measuring 208V to ground on a 120/240V system) must be durability
finished or tagged with an orange outer finish.
8. Which state agency is responsible for enforcing workplace safety rules and site
inspections for electrical contractors in California?
A. CSLB
B. Cal/OSHA
C. EPA
D. EDD
Rationale: The Division of Occupational Safety and Health (DOSH), commonly known as
Cal/OSHA, enforces workplace safety standards, inspects construction job sites, and issues
, citations for safety violations across California. CSLB licenses contractors but does not
administer workplace safety inspections.
9. What is the maximum allowable fill percentage for a single conductor installed inside a
2-inch conduit run?
A. 31%
B. 40%
C. 53%
D. 60%
Rationale: NEC Chapter 9, Table 1 dictates conduit fill percentages. A single conductor placed
inside any raceway is allowed up to 53% conduit fill. For two conductors, the limit drops to
31%, and for three or more conductors, the maximum allowable fill is 40%.
10. A home improvement contract must contain a statutory notice regarding the buyer's
right to cancel. What is the standard cancellation period for a non-emergency residential
remodeling contract in California?
A. 24 hours
B. 3 business days
C. 5 business days
D. 10 business days
Rationale: Under California Civil Code Section 1689.5, consumers have a statutory right to
cancel a home improvement contract within 3 business days after signing. Note that for
senior citizens (age 65+) or during declared state emergencies, specific rules may extend this
period to 5 business days.
11. What is the minimum size copper equipment grounding conductor required for a
circuit protected by a 100-ampere overcurrent protective device?
A. 10 AWG
B. 8 AWG
C. 6 AWG
D. 4 AWG
Questions And Answers| Exam Prep |All Questions And
Answers 2026/2027 | Verified Answers Plus Rationales |
Graded Q&A Comprehensive Study Guide | Verified Latest
2027
1. According to California Contractors License Law, what is the maximum initial down
payment a licensed electrical contractor can legally require for a residential home
improvement contract?
A. $1,000 or 10% of the contract price, whichever is less
B. $1,000 or 10% of the contract price, whichever is greater
C. 25% of the total contract price
D. $500 or 5% of the contract price, whichever is less
Rationale: Under California Business and Professions Code Section 7159, the down payment
for any residential home improvement contract cannot exceed $1,000 or 10% of the total
contract price, whichever amount is less. Requiring more than this legal threshold is a
misdemeanor offense subject to disciplinary action by the CSLB.
2. A C-10 contractor is performing a commercial tenant improvement project. What is the
minimum depth required for underground direct-burial UF cable operating at 120V and
protected by a 20A GFCI circuit breaker in a location not subject to vehicular traffic?
A. 24 inches
B. 18 inches
C. 12 inches
D. 6 inches
Rationale: According to NEC Table 300.5, Column 4, residential or commercial 120V branch
circuits rated 20A or less and protected by a GFCI before entering the ground require a
minimum burial depth of only 12 inches when located in areas not subject to vehicular traffic.
Standard non-GFCI direct-burial cables require 24 inches.
3. An electrical contractor hires a new journey-level electrician. Within how many days
must the contractor report the hiring to their Workers' Compensation insurance carrier to
maintain complete regulatory compliance?
,A. 10 days
B. 30 days
C. Reporting guidelines are governed by policy terms, but all wages must be reported on the
periodic payroll audit
D. 60 days
Rationale: While new employees must be registered with the California Employment
Development Department (EDD) within 20 days via Form DE 34, Workers' Compensation
policy compliance requires accurate reporting of all payroll during mandatory periodic policy
audits, rather than single-employee initial notifications unless specifically dictated by insurer
policy terms.
4. When calculating total service load for a commercial building, what multiplier must be
applied to continuous loads under the provisions of NEC Article 210?
A. 100%
B. 115%
C. 125%
D. 140%
Rationale: NEC 210.20(A) mandates that branch circuit overcurrent protective devices and
conductors feeding continuous loads (loads operating continuously for 3 hours or more) must
be sized at not less than 125% of the continuous load plus 100% of the non-continuous load.
5. What is the maximum distance allowed between supporting straps for a 1-inch rigid
metal conduit (RMC) run along a flat masonry wall?
A. 6 feet
B. 8 feet
C. 10 feet
D. 12 feet
Rationale: Pursuant to NEC 344.30(A), Rigid Metal Conduit (RMC) must be supported at
intervals not exceeding 10 feet. Furthermore, it must be securely fastened within 3 feet of
each conduit termination, box, or enclosure.
,6. Under California mechanics' lien law, within how many days must a subcontractor file a
Preliminary 20-Day Notice after starting work to preserve their full mechanics' lien rights?
A. 10 days
B. 20 days
C. 30 days
D. 60 days
Rationale: California Civil Code requires sub-tier contractors to serve a Preliminary 20-Day
Notice within 20 days of first furnishing labor, materials, or equipment to a jobsite. Serving it
later limits lien rights strictly to work provided during the 20 days prior to service and
thereafter.
7. In a standard 3-phase, 4-wire delta system (high-leg delta), what is the color
identification required by the NEC for the conductor with the higher voltage to ground?
A. Red
B. Orange
C. Yellow
D. Blue
Rationale: NEC 110.15 specifies that on a 4-wire, delta-connected system where the midpoint
of one phase winding is grounded, the conductor having the higher phase voltage to ground
(the "high-leg", typically measuring 208V to ground on a 120/240V system) must be durability
finished or tagged with an orange outer finish.
8. Which state agency is responsible for enforcing workplace safety rules and site
inspections for electrical contractors in California?
A. CSLB
B. Cal/OSHA
C. EPA
D. EDD
Rationale: The Division of Occupational Safety and Health (DOSH), commonly known as
Cal/OSHA, enforces workplace safety standards, inspects construction job sites, and issues
, citations for safety violations across California. CSLB licenses contractors but does not
administer workplace safety inspections.
9. What is the maximum allowable fill percentage for a single conductor installed inside a
2-inch conduit run?
A. 31%
B. 40%
C. 53%
D. 60%
Rationale: NEC Chapter 9, Table 1 dictates conduit fill percentages. A single conductor placed
inside any raceway is allowed up to 53% conduit fill. For two conductors, the limit drops to
31%, and for three or more conductors, the maximum allowable fill is 40%.
10. A home improvement contract must contain a statutory notice regarding the buyer's
right to cancel. What is the standard cancellation period for a non-emergency residential
remodeling contract in California?
A. 24 hours
B. 3 business days
C. 5 business days
D. 10 business days
Rationale: Under California Civil Code Section 1689.5, consumers have a statutory right to
cancel a home improvement contract within 3 business days after signing. Note that for
senior citizens (age 65+) or during declared state emergencies, specific rules may extend this
period to 5 business days.
11. What is the minimum size copper equipment grounding conductor required for a
circuit protected by a 100-ampere overcurrent protective device?
A. 10 AWG
B. 8 AWG
C. 6 AWG
D. 4 AWG
