25 multiple-choice questions for the OSHA Electrical Safety (Subpart S) Practice Test. Pick an answer to see the rule behind it, quoted from the official source.
1. A pipe carrying water is located near industrial control assemblies. Under what condition is this allowed?
Answer: If protection is provided to avoid damage from condensation leaks and breaks. Foreign pipes are generally prohibited nearby unless protection is provided against leaks and breaks.
29 CFR § 1910.303(h): “Pipes or ducts that are foreign to the electrical installation and that require periodic maintenance or whose malfunction would endanger the operation of the electrical system may not be located in the vicinity of service equipment, metal-enclosed power switchgear, or industrial control assemblies. Protection shall be provided where necessary to avoid damage from condensation leaks and breaks in such foreign systems.”
2. When inspecting a flexible cord used for general wiring, what marking requirement must the cord meet to be considered compliant?
Answer: It must be durably marked on the surface at intervals not exceeding 24 inches with type, size, and number of conductors. The rule specifies that flexible cords must be durably marked at intervals no greater than 24 inches with the type designation, size, and number of conductors.
29 CFR § 1910.305(g): “Types S, SC, SCE, SCT, SE, SEO, SEOO, SJ, SJE, SJEO, SJEOO, SJO, SJT, SJTO, SJTOO, SO, SOO, ST, STO, and STOO flexible cords and Types G, G-GC, PPE, and W flexible cables shall be durably marked on the surface at intervals not exceeding 610 mm (24 in.) with the type designation, size, and number of conductors.”
3. An electrician is installing a heavy-duty lampholder on a branch circuit rated at 30 amperes. The lampholder is of the admedium type. What is the minimum wattage rating required for this lampholder?
Answer: 660 watts. The regulation specifies that admedium type heavy-duty lampholders must be rated for at least 660 watts.
29 CFR § 1910.304(b): “A heavy-duty lampholder shall have a rating of not less than 660 watts if of the admedium type and not less than 750 watts if of any other type”
4. Before using a flexible extension cord set for portable equipment, what inspection is required by the worker?
Answer: Visual inspection for external defects and evidence of possible internal damage. Workers must visually inspect cords before use on any shift to identify both external defects and signs of internal damage like pinching or crushing.
29 CFR § 1910.334(a): “Portable cord- and plug-connected equipment and flexible cord sets (extension cords) shall be visually inspected before use on any shift for external defects (such as loose parts, deformed and missing pins, or damage to outer jacket or insulation) and for evidence of possible internal damage (such as pinched or crushed outer jacket).”
5. A worker is evaluating a location where easily ignitible fibers are stored or handled, but not in the process of manufacture. How is this location classified?
Answer: Class III, Division 2. The rule defines Class III, Division 2 as a location where easily ignitible fibers are stored or handled, except in the process of manufacture.
29 CFR § 1926.449: “Class III, Division 2. A Class III, Division 2 location is a location in which easily ignitible fibers are stored or handled, except in process of manufacture.”
6. An electrician is routing Class 2 circuit conductors in the same raceway as power-limited fire alarm (PLFA) circuit conductors. What condition must be met regarding the insulation of the Class 2 conductors?
Answer: The insulation of Class 2 circuit conductors must be at least that needed for the power-limited fire alarm circuits. Mixing Class 2 and PLFA conductors is permitted only if the Class 2 insulation rating matches or exceeds the requirement for the PLFA circuits.
29 CFR § 1910.308(d): “provided that the insulation of Class 2 circuit conductors in the cable, enclosure, or raceway is at least that needed for the power-limited fire alarm circuits”
7. An electrician is installing a disconnecting means for a motor controller. The motor and the driven machinery are not in sight from the controller location. To comply with safety requirements, which of the following conditions must be met?
Answer: The controller disconnecting means must be capable of being locked in the open position. When the motor and machinery are out of sight from the controller, the regulation requires the disconnect to be lockable in the open position to ensure safe isolation.
29 CFR § 1926.405(j): “If a motor and the driven machinery are not in sight from the controller location, the installation shall comply with one of the following conditions: (1) The controller disconnecting means shall be capable of being locked in the open position.”
8. When using portable electric equipment within the cell line working zone, under which specific condition are the frames and enclosures permitted to be grounded?
Answer: If the cell line circuit voltage does not exceed 200 volts DC or the frames are guarded. Grounding of frames is generally prohibited in the working zone unless the voltage is low (≤200 V DC) or the frames are physically guarded.
29 CFR § 1910.306(h): “The frames and enclosures of portable electric equipment used within the cell line working zone may not be grounded, unless the cell line circuit voltage does not exceed 200 volts DC or the frames are guarded.”
9. A technician is routing power-limited fire alarm (PLFA) circuit conductors through a raceway that also contains electric light and power conductors. What is the minimum separation distance required between these conductors unless an equally protective method is used?
Answer: 2 inches. The rule mandates a minimum separation of 2 inches (50.8 mm) between PLFA conductors and higher-voltage circuits like electric light and power.
29 CFR § 1910.308(d): “Power-limited fire alarm circuit conductors shall be separated at least 50.8 mm (2 in.) from conductors of any electric light, power, Class 1, nonpower-limited fire alarm, or medium power network-powered broadband communications circuits unless a special and equally protective method of conductor separation is employed.”
10. An electrician is installing a new power outlet assembly for mobile construction equipment. According to the definition of 'Power outlet,' which of the following components is included as part of this enclosed assembly?
Answer: Watt-hour meter mounting means. The definition lists watt-hour meter mounting means as a component that may be included in the power outlet assembly.
29 CFR § 1926.449: “Power outlet. An enclosed assembly which may include receptacles, circuit breakers, fuseholders, fused switches, buses and watt-hour meter mounting means; intended to serve as a means for distributing power required to operate mobile or temporarily installed equipment.”
11. An electrician is installing a piece of equipment that produces arcs and sparks during ordinary operation. To prevent fire hazards, what must be done regarding the surrounding environment?
Answer: The arcing parts must be enclosed or separated and isolated from all combustible material. The rule requires that sources of ignition like arcs and sparks be physically separated or enclosed to keep them away from any combustible materials.
29 CFR § 1910.303(d): “Parts of electric equipment that in ordinary operation produce arcs, sparks, flames, or molten metal shall be enclosed or separated and isolated from all combustible material.”
12. An industrial worker is installing a device intended to protect personnel by deenergizing a circuit when current to ground exceeds a predetermined value lower than that required to trip the overcurrent device. What is this device called?
Answer: Ground-fault circuit-interrupter. The rule defines the ground-fault circuit-interrupter as the specific device designed for personnel protection by deenergizing circuits upon detecting ground faults below the overcurrent device's trip threshold.
29 CFR § 1910.399: “Ground-fault circuit-interrupter. A device intended for the protection of personnel that functions to deenergize a circuit or a portion of a circuit within an established period of time when a current to ground exceeds some predetermined value that is less than that required to operate the overcurrent protective device of the supply circuit.”
13. In an industrial facility with an integrated electrical system requiring orderly shutdown, where may overcurrent devices critical to the system be located if they are not readily accessible to employees?
Answer: They may be located with mounting heights to ensure security from operation by nonqualified persons. The rule allows these devices to be less accessible if mounted at heights that prevent nonqualified persons from operating them.
29 CFR § 1910.308(g): “Overcurrent devices that are critical to integrated electrical systems need not be readily accessible to employees as required by § 1910.304(f)(1)(iv) if they are located with mounting heights to ensure security from operation by nonqualified persons.”
14. An industrial worker is installing a fuse rated for over 600 volts. According to the definition, what component is heated and severed by the passage of overcurrent to open the circuit?
Answer: The circuit opening fusible part. The definition states that the specific part of the fuse that heats and severs to open the circuit is the circuit opening fusible part.
29 CFR § 1910.399: “Fuse. (Over 600 volts, nominal.) An overcurrent protective device with a circuit opening fusible part that is heated and severed by the passage of overcurrent through it.”
15. An electrician is reviewing the installation of a new circuit. To identify the 'branch circuit' conductors, which segment of the circuit should the electrician inspect?
Answer: The conductors between the final overcurrent device protecting the circuit and the outlet(s). The rule defines a branch circuit as the conductors located between the final overcurrent device and the outlets.
29 CFR § 1926.449: “Branch circuit. The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s).”
16. An electrician is setting up circuits to supply power to ungrounded receptacles for hand-held, cord- and plug-connected equipment in a cell line working zone. Which requirement must these circuits meet?
Answer: They must be supplied through isolating transformers with a secondary voltage not exceeding 300 volts between conductors. The rule specifies that isolating transformers used for these circuits must have a secondary voltage not exceeding 300 volts between conductors.
29 CFR § 1910.306(h): “The secondary voltage of the isolating transformers may not exceed 300 volts between conductors; and (D) All circuits supplied from the secondaries shall be ungrounded and shall have an approved overcurrent device of proper rating in each conductor.”
17. An electrician is installing a foot-operated switch to control power to a piece of equipment. What specific safety feature must be provided for the switch contact button?
Answer: A shield over the contact button to avoid accidental closing of the switch. The regulation mandates a shield over the contact button for foot-operated switches to prevent accidental activation.
29 CFR § 1910.306(g): “Switches operated by foot pressure shall be provided with a shield over the contact button to avoid accidental closing of the switch.”
18. An electrician is installing a new 120/240V single-phase, three-wire service for a commercial building. According to OSHA grounding requirements for systems to be grounded, which conductor must be grounded?
Answer: The neutral conductor. For single-phase, three-wire systems, the regulation requires the neutral conductor to be the grounded conductor.
29 CFR § 1910.304(g): “The neutral conductor of a single-phase, three-wire system shall be grounded;”
19. A worker is assigned to remove a fuse from a panel where the fuse terminals are currently energized. What specific equipment must be used for this task?
Answer: Fuse handling equipment insulated for the circuit voltage. OSHA requires the specific use of fuse handling equipment that is insulated for the circuit voltage when the terminals are live.
29 CFR § 1910.335(a): “Fuse handling equipment, insulated for the circuit voltage, shall be used to remove or install fuses when the fuse terminals are energized.”
20. A technician is installing a locknut and bushing on a conduit entry. According to the definitions, how are these accessories classified regarding their primary function?
Answer: As fittings intended primarily to perform a mechanical rather than an electrical function. The rule classifies locknuts and bushings as fittings because their primary purpose is mechanical rather than electrical.
29 CFR § 1910.399: “Fitting. An accessory such as a locknut, bushing, or other part of a wiring system that is intended primarily to perform a mechanical rather than an electrical function.”
21. An industrial electrician is verifying that equipment meets safety standards. Under the definition of 'Certified', what specific condition must be met regarding the testing laboratory?
Answer: The laboratory must be a nationally recognized testing laboratory. The definition requires that the testing or periodic inspection be performed by a 'nationally recognized testing laboratory'.
29 CFR § 1910.399: “Certified. Equipment is “certified” if it bears a label, tag, or other record of certification that the equipment: (1) Has been tested and found by a nationally recognized testing laboratory to meet nationally recognized standards or to be safe for use in a specified manner; or (2) Is of a kind whose production is periodically inspected by a nationally recognized testing laboratory and is accepted by the laboratory as safe for its intended use.”
22. A worker is identifying equipment that has been included in a published list by a qualified testing laboratory, stating it meets appropriate standards. What is the specific term for this equipment?
Answer: Listed. The definition of 'Listed' specifically refers to equipment included in a published list by a qualified testing laboratory, whereas 'Labeled' refers to a physical mark or symbol attached to the equipment.
29 CFR § 1926.449: “Listed. Equipment or materials included in a list published by a qualified testing laboratory whose listing states either that the equipment or material meets appropriate standards or has been tested and found suitable for use in a specified manner.”
23. An electrician is installing a panel with exposed live parts operating at 50 volts or more in an open warehouse area. To comply with guarding requirements without using a locked room or partition, what is the minimum elevation required above the working surface?
Answer: 8 feet (2.44 m). The regulation sets 8 feet as the minimum elevation to guard against accidental contact when other enclosure methods are not used.
29 CFR § 1926.403(i): “By elevation of 8 feet (2.44 m) or more above the floor or other working surface and so installed as to exclude unqualified persons.”
24. An electrician needs to repair a hard service flexible cord (No. 12 or larger) that has been damaged. Under what condition does OSHA allow this repair?
Answer: If the splice retains the insulation, outer sheath properties, and usage characteristics of the original cord. Repairs are only allowed for hard service cords No. 12 or larger if the splice maintains the original cord's protective and usage characteristics.
29 CFR § 1926.405(g): “Hard service flexible cords No. 12 or larger may be repaired if spliced so that the splice retains the insulation, outer sheath properties, and usage characteristics of the cord being spliced.”
25. An electrician is wiring a vehicle-mounted generator system. The generator frame is bonded to the vehicle frame, and the generator supplies only equipment located on the vehicle. To use the vehicle frame as the grounding electrode, what must be true regarding the equipment grounding conductor terminals of the receptacles?
Answer: They are bonded to the generator frame. The regulation specifically requires that receptacle grounding terminals be bonded to the generator frame, not directly to the vehicle frame, even when the generator is vehicle-mounted.
29 CFR § 1926.404(f): “The noncurrent-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame”