OSHA Electrical Safety Quiz — 29 CFR 1926.400-449 Practice (Construction) — Page 2 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. (Page 2 of 4)
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Q11/ 40
A construction site uses portable generators for temporary power. A worker plugs a circular saw directly into a generator's 120V outlet. The generator is not equipped with GFCI protection. The worker is standing on damp concrete. What is required?
✅ Correct Answer: B
1926.404(b)(1)(i): all 120-volt, single-phase, 15- and 20-ampere receptacle outlets on construction sites, which are not a part of the permanent wiring of the building or structure and which are in use by employees, shall have ground-fault circuit interrupter protection. Alternatively, 1926.404(b)(1)(ii) allows an Assured Equipment Grounding Conductor Program. The damp concrete increases the risk of ground-fault electrocution dramatically.
Q12/ 40
An excavator operator is digging near a utility marking that says 'UNDERGROUND ELECTRIC — 13.2 kV.' The one-call center marked the line, but the marks are 3 days old and partially faded. The operator starts digging 3 feet from the faded marks. The bucket strikes the cable. What should have been done?
✅ Correct Answer: B
1926.651(b)(1): the estimated location of utility installations shall be determined prior to opening the excavation. Hand-digging (pot-holing, vacuum excavation) to physically expose the utility is the industry standard for verification before mechanical excavation within the tolerance zone (typically 18-24 inches from markings). Faded marks introduce uncertainty. Striking a 13.2 kV line can cause catastrophic arc flash and electrocution.
Q13/ 40
A construction electrician installs temporary wiring for job-site lighting. The wiring is type NM (Romex) cable run along the surface of studs at 6 feet height, secured every 6 feet with staples. The run is 40 feet long, powering 4 LED temporary lights. Is this compliant?
✅ Correct Answer: B
1926.405(a)(2)(ii)(A): NM cable used for temporary wiring shall be protected from damage. NM cable's plastic sheathing is easily cut by sharp objects and crushed by ladders. At 6 feet on studs in active construction, the cable is in the damage zone from material handling and scissor lifts. Acceptable protection includes running NM through stud holes (protected on both sides), using armored cable (MC), or installing rigid conduit in exposed areas.
Q14/ 40
A crew working on a highway lighting project is replacing a pole-mounted light fixture near an active 7,200V overhead power line. The crew uses a metal extension ladder. The nearest energized conductor is 4 feet horizontally from the work position. What clearance must be maintained?
✅ Correct Answer: B
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 circuit. 1926.1408 Table A specifies minimum clearance distances: 10 feet for lines ≤50 kV. A metal ladder 4 feet from a 7,200V line is extremely dangerous — if the ladder slips or tips, it can contact the line, killing everyone on or near the ladder.
Q15/ 40
A jobsite has been experiencing repeated nuisance tripping of a GFCI on a circuit powering a worm-drive circular saw. The foreman instructs a worker to replace the GFCI outlet with a standard outlet 'just for today' until a new GFCI can be installed. Is this acceptable?
✅ Correct Answer: B
1926.404(b)(1)(i): GFCI protection is mandatory for all 120V receptacle outlets on construction sites. The foreman's instruction to remove a safety device is a willful violation under the OSH Act. Rather than bypassing the GFCI, the foreman should investigate the cause — the GFCI may be correctly tripping because the saw has a ground fault. Nuisance tripping is a symptom of a ground fault, not a defect in the GFCI.
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Q16/ 40
An electrician is working on a 480V panelboard, replacing a circuit breaker. The electrician turns off the main breaker but does not verify zero voltage, lock out, or tag it. Another worker turns the main back on. The electrician is shocked. What LOTO violations occurred?
✅ Correct Answer: B
1926.417(b): equipment or circuits that are de-energized shall be rendered inoperative (locked out and tagged). 1926.416(a)(1): employees must be protected by de-energizing and grounding the circuit. Simply turning off a breaker without LOTO provides zero protection — anyone can turn it back on. Verification of zero energy state (testing with a known-working meter before and after) is critical.
Q17/ 40
On a bridge renovation project, workers are cutting rebar with an electric grinder. The grinder's 3-prong plug has the ground pin broken off. The tool is plugged into a GFCI-protected extension cord. Is this acceptable?
✅ Correct Answer: B
1926.404(f)(3): the equipment grounding conductor provides a low-resistance path for fault current to trip the overcurrent device. The GFCI detects current imbalance (leakage) and trips at 5mA. They serve different functions. A tool with a missing ground pin has NO protection against an internal fault energizing the tool frame — the GFCI won't trip until current leaks through a person (at which point the person IS the ground path, receiving up to a 5mA shock before the GFCI trips).
Q18/ 40
A temporary service (power pole) is installed on a construction site. The panel is mounted on a wood post at 72 inches above grade. The panel door is missing — breakers are exposed to weather. Workers plug in tools at this panel daily. It has rained. What violations?
✅ Correct Answer: B
1926.403(i)(2): live parts of electrical equipment shall be guarded against accidental contact. 1926.405(b)(1): cabinets and panelboards shall be mounted in dry locations and shall be weatherproof when installed in wet locations. Exposed breakers with no dead front allow workers to accidentally contact energized bus bars. Rain dramatically increases shock risk — water provides a conductive path.
Q19/ 40
A construction crew is using multiple 100-foot extension cords daisy-chained to power tools 400 feet from the nearest outlet. The cords are 14-gauge, rated for 15A. The total connected load is 13A. What are the concerns?
✅ Correct Answer: B
1926.405(a)(2)(ii)(J): extension cords shall be maintained in good condition. While not explicitly prohibiting daisy-chaining, OSHA interprets 'approved wiring methods' as requiring adequate gauge for the run length. 14-gauge at 400 feet carrying 13A will drop 20+ volts, causing tools to run at ~100V. Low voltage increases current draw, overheating motors. Each connector junction is a failure point and trip hazard. The solution is a single 10-gauge cord of adequate length or a temporary distribution panel closer to the work area.
Q20/ 40
On a construction site, a metal junction box for temporary power is mounted on a metal stud wall. The box is energized (has live wires inside) but the box itself is not grounded. The circuit does have GFCI protection. A worker touches the box while standing on wet ground and receives a shock. Why?
✅ Correct Answer: B
1926.404(f)(3): all metal enclosures for circuits and equipment shall be grounded. The equipment grounding conductor provides a low-impedance path that allows fault current to flow, tripping the breaker or GFCI. Without it, if a hot wire touches the ungrounded metal box, the box becomes energized at full line voltage (120V) but no current flows — until someone touches it. The GFCI detects current imbalance but only when current IS flowing. A GFCI does not prevent the initial shock — it limits the duration to 20-30 milliseconds after detecting 5mA+ of leakage.