100+ Free CSLB C-10 Electrical Practice Questions

Explanation: Per CEC Table 220.42, the first 3,000 VA of general lighting and small appliance load is calculated at 100% (3,000 VA). The remaining load of 8,700 VA (11,700 VA - 3,000 VA) is calculated at 35%, which equals 3,045 VA. Adding 3,000 VA and 3,045 VA yields a net calculated demand load of 6,045 VA.

Explanation: Voltage drop for a single-phase two-wire circuit is calculated using VD = (2 x K x I x L) / CM. Substituting the values yields VD = (2 x 12.9 x 20 A x 150 ft) / 10,380 CM = 77,400 / 10,380 = 7.46 V. CEC Informational Notes recommend limiting branch circuit voltage drop to 3% (7.2V on 240V).

Explanation: Three-phase voltage drop is calculated using VD = (1.732 x K x I x L) / CM. Substituting values gives VD = (1.732 x 12.9 x 100 A x 300 ft) / 105,600 CM = 670,284 / 105,600 = 6.35 V. Dividing 6.35 V by 480 V gives 0.0132 or 1.32%, which complies with the CEC 3% feeder limit recommendation.

Explanation: Per CEC Table 220.55 Column C, the maximum demand for four 12 kW household electric ranges is listed directly as 17 kW. Because all ranges are rated 12 kW (not exceeding 12 kW), no additional 5% increase per kW is required.

Explanation: CEC Table 220.56 specifies demand factors for commercial kitchen equipment. For 1 to 2 units the factor is 100%, 3 units is 90%, 4 units is 80%, 5 units is 70%, and for 6 or more units, the demand factor is 65% of total connected load.

Explanation: Standard electrical plan symbols per ANSI/IEEE standards use 'S' for a single-pole switch, 'S3' for a three-way switch, and 'S4' for a four-way switch. Three-way switches permit controlling a lighting load from two distinct locations.

Explanation: CEC Chapter 9, Table 1 specifies that one conductor allows 53% fill, two conductors allow 31% fill, and three or more conductors allow a maximum of 40% conduit fill of the internal cross-sectional area of the raceway. The 40% limit for three or more conductors balances heat dissipation needs against practical wire-pulling friction. A higher 60% fill is permitted only for conduit nipples 24 inches or shorter between enclosures, where heat and pulling concerns are minimal.

Explanation: Installing 400 feet of conduit at 1.5 labor hours per 100 feet requires (400 / 100) x 1.5 = 6.0 total labor hours. Multiplying 6.0 hours by the $85/hour fully burdened labor rate yields a total direct labor cost of $510.

Explanation: California Title 24 Part 6 Section 130.1(c) mandates that nonresidential indoor lighting systems must have occupant-accessible manual controls plus automatic shut-off controls (such as occupancy sensors or automatic time-switch controls) to reduce energy consumption.

Explanation: CEC 215.3 and 230.42 require service overcurrent devices and conductors to be sized at not less than 125% of continuous loads plus 100% of non-continuous loads. Calculation: (160 A x 1.25) + 80 A = 200 A + 80 A = 280 A.