OSHA Electrical Safety Quiz — 29 CFR 1926.400-449 Practice (Construction) — Page 1 of 4
Free OSHA 30-Hour Construction electrical safety practice test with 40 realistic scenarios. GFCI, AEGCP, temporary wiring, overhead line clearance, lockout/tagout, hazardous locations, and portable generator safety with 29 CFR 1926 Subpart K references.
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Q1/ 40
A crew is using a portable electric hammer drill on a commercial construction site. The drill is plugged into a temporary receptacle on a 120V, 20A circuit that was installed for the job. A worker receives a mild shock when the drill's metal casing becomes energized. The circuit has a standard circuit breaker installed. What does 29 CFR 1926.404(b)(1) require?
✅ Correct Answer: B
1926.404(b)(1)(i): the employer shall use either ground fault circuit interrupters (GFCI) OR an Assured Equipment Grounding Conductor Program (AEGCP) to protect employees on construction sites. A standard circuit breaker only trips at ~20A overcurrent — it will NOT detect the 5-30mA ground fault that can cause electrocution. The worker was shocked because no GFCI was present. The AEGCP alternative requires documented daily testing of all cords and tools by a competent person.
Q2/ 40
An excavator operator is digging a trench near a marked underground electrical duct bank carrying 480V feeders to a building. The markings show the duct bank at 36 inches depth. The operator is using a 24-inch bucket. What does OSHA 1926.651(b) require before mechanical excavation near this electrical hazard?
✅ Correct Answer: B
1926.651(b)(2): while the excavation is open, underground installations shall be protected, supported, or removed as necessary to safeguard employees. 1926.651(b)(1): the estimated location of utility installations shall be determined prior to opening the excavation. Standard industry practice (recognized by OSHA) requires hand-digging or vacuum excavation within 24 inches of marked utility locations. Striking a 480V line with an excavator can cause arc flash and electrocution of the operator.
Q3/ 40
A scissor lift is being repositioned inside a warehouse under construction. The operator raises the platform near overhead fluorescent light fixtures with exposed wiring at 277V. The top rail of the lift comes within 18 inches of the energized conductors. Is this acceptable?
✅ Correct Answer: C
1926.416(a)(1): no employer shall permit an employee to work in such proximity to any part of an electric power circuit that the employee could contact the power circuit in the course of work, unless the employee is protected against electric shock by de-energizing the circuit and grounding it or by guarding it effectively. 277V lighting circuits are lethal — they cause more electrocution fatalities than higher voltages in commercial construction. At 18 inches, any inadvertent movement or metal tool contact could be fatal.
Q4/ 40
A construction electrician is installing temporary wiring on a jobsite. The wiring runs along the ground through a high-traffic doorway used by material carts. What does 29 CFR 1926.405(a)(2) require for this temporary wiring installation?
✅ Correct Answer: A
1926.405(a)(2)(ii)(J): extension cords and cables shall be protected from damage. Sharp corners and projections shall be avoided. Flexible cords and cables shall be protected from accidental damage, as might be caused by sharp corners, projections, and doorways or other pinch points. Running cords across a doorway without a protective ramp (or overhead routing) creates trip hazards AND risks cutting the cord insulation, causing energized conductors to be exposed.
Q5/ 40
A site superintendent needs to use a portable generator during the rough-in phase before permanent power is available. The generator is 5kW, 120/240V. Workers will use drills, saws, and a small welder. What grounding and GFCI requirements apply under OSHA Subpart K?
✅ Correct Answer: B
1926.404(f)(3): for portable generators, the frame of the generator need not be grounded (may serve as the grounding electrode) IF: (i) the generator supplies only equipment mounted on the generator and/or cord-and-plug-connected equipment through receptacles mounted on the generator, and (ii) the noncurrent-carrying metal parts of equipment and the equipment grounding terminals of the receptacles are bonded to the generator frame. However, 1926.404(b)(1) still requires GFCI protection for all 120V, 15/20A receptacles on construction sites. A generator with integral GFCI receptacles is the compliant solution.
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Q6/ 40
A renovation project requires cutting into an existing wall. The foreman tells a laborer to use a reciprocating saw to cut through the drywall, saying 'the power should be off on that wall.' The laborer hits a live 120V Romex cable, causing a short circuit but no injury. What did OSHA require that the foreman failed to do?
✅ Correct Answer: B
1926.417(a): controls shall be tagged. Equipment or circuits that are de-energized shall be rendered inoperative and shall have tags attached at all points where such equipment or circuits can be energized. 1926.417(b): tags must clearly state 'DANGER — DO NOT ENERGIZE.' The foreman's verbal statement is not LOTO. Additionally, 1926.416(a)(1) requires circuits to be DE-ENERGIZED and VISUALLY VERIFIED before work begins. 'Should be off' is not verification — a non-contact voltage tester and meter confirmation are the minimum standard of care.
Q7/ 40
On a jobsite, workers use multiple 100-foot extension cords daisy-chained together to reach a work area. The total run is 400 feet of 14 AWG cord powering a 15A miter saw. The saw motor runs slowly and the cord feels warm. What violations exist?
✅ Correct Answer: B
1926.405(a)(2)(ii)(B): extension cord sets used with portable electric tools must be of three-wire type and shall be designed for hard or extra-hard usage. At 400 feet of 14 AWG, the voltage drop at 15A exceeds 10% — the saw motor is undervolted, drawing higher current, overheating both the motor windings and the cord. This is a fire hazard. The cord's warmth indicates resistance heating exceeding the cord's ampacity for that length. Daisy-chaining also introduces multiple connection points, each a potential failure/arcing location.
Q8/ 40
A metal extension ladder is being used by a window installer working near the service entrance of a building. The service drop conductors (120/240V, uninsulated triplex) are approximately 4 feet from the work area. The installer is on an aluminum ladder. What is the minimum safe practice?
✅ Correct Answer: B
1926.416(a)(1): employees must not work in proximity to energized circuits without protection. 1926.1053(b)(12): ladders with conductive side rails (aluminum) shall not be used where the employee or ladder could contact exposed energized electrical equipment. Service drop conductors are often bare (uninsulated) where they connect to the weatherhead. A 4-foot working distance while handling metal window frames is dangerously close. The fiberglass ladder is the minimum first step, but the clearance must still be maintained.
Q9/ 40
A jobsite has been experiencing repeated GFCI tripping on a circuit powering multiple tools. The foreman tells the electrician to 'swap in a regular outlet until we finish this concrete pour.' The electrician complies. An OSHA inspector arrives two hours later. What is the violation?
✅ Correct Answer: B
1926.404(b)(1)(i) requires GFCI protection (or AEGCP) for all 120V, 15/20A construction receptacles — no exception for concrete pours. The foreman knowingly caused the removal of a required safety device. This meets OSHA's definition of a willful violation, which carries a maximum penalty of $161,323 per violation (2025 penalties). The GFCI was tripping because of a ground fault — the safety device was doing its job. Defeating it to 'finish the pour' exposes every worker on that circuit to electrocution.
Q10/ 40
Workers are using a 240V arc welder on a steel bridge project. The welder's case is metallic. The power cord is a 3-wire (2 hots + ground) SOOW cable. The ground pin on the plug has been cut off because 'the generator receptacle doesn't have a ground slot.' What does 1926.404(b)(1)(iii) require regarding equipment grounding?
✅ Correct Answer: B
1926.404(b)(1)(iii): the equipment grounding conductor program (AEGCP) requires all cord sets, receptacles, and cord-and-plug-connected equipment to have an intact equipment grounding conductor. 1926.404(f)(6): the path to ground from circuits, equipment, and enclosures shall be permanent, continuous, and effective. Removing the ground pin leaves the welder's metal case floating — if the hot conductor touches the case internally, the entire case becomes energized at 120V to ground. Any worker touching the case and any grounded surface (bridge steel) completes the circuit. This has caused multiple construction electrocution fatalities.