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 worker is installing a portable cable over 600 volts to supply power to mobile equipment. What is the minimum conductor size required for the main conductors?
Answer: No. 8 or larger conductors employing flexible stranding. For portable cables over 600 volts, the regulation mandates that main conductors must be No. 8 or larger with flexible stranding.
29 CFR § 1910.305(h): “Multiconductor portable cable for use in supplying power to portable or mobile equipment at over 600 volts, nominal, shall consist of No. 8 or larger conductors employing flexible stranding.”
2. An electrician is guarding live parts operating at 50 volts or more against accidental contact. Which of the following is a compliant method for guarding these parts if they are not in an approved cabinet?
Answer: Placing them on a suitable balcony, gallery, or platform so elevated and otherwise located as to prevent access by unqualified persons. The regulation lists placement on an elevated balcony, gallery, or platform as an approved method to prevent access by unqualified persons.
29 CFR § 1910.303(g): “By placement on a suitable balcony, gallery, or platform so elevated and otherwise located as to prevent access by unqualified persons; or”
3. A worker is preparing to service a circuit and needs to verify the status of the conductors. What is the precise definition of 'Deenergized' that the worker must confirm before proceeding?
Answer: The circuit is free from any electrical connection to a source of potential difference and from electrical charge; not having a potential different from that of the earth. To be considered deenergized, the circuit must have no connection to a power source and no residual charge, matching the earth's potential.
29 CFR § 1910.399: “Deenergized. Free from any electrical connection to a source of potential difference and from electrical charge; not having a potential different from that of the earth.”
4. An electrician is installing fixed equipment in a wet location that is not isolated. According to OSHA standards, under which condition must the exposed noncurrent-carrying metal parts of this equipment be grounded?
Answer: If the equipment is located in a wet or damp location and not isolated. The regulation lists being in a wet or damp location and not isolated as a condition requiring grounding for exposed noncurrent-carrying metal parts of fixed equipment.
5. An electrician is installing fused cutouts in a transformer vault. Which requirement applies to the type of cutout used in this location?
Answer: They must be of a type identified for the purpose. The regulation requires that fused cutouts in transformer vaults be specifically identified for that purpose, while distribution cutouts are generally prohibited in such enclosed spaces.
29 CFR § 1910.308(a): “Fused cutouts installed in buildings or transformer vaults shall be of a type identified for the purpose.”
6. An electrician is installing a hoist in a facility where controls are enclosed in cabinets. To ensure safe access for examination and maintenance while the parts are alive, what is the minimum required dimension of the working space in the direction of access to live parts?
Answer: 2 feet 6 inches (762 mm). The regulation sets the minimum clearance for working space near live parts at 2 feet 6 inches.
29 CFR § 1926.406(a): “The dimension of the working space in the direction of access to live parts which may require examination, adjustment, servicing, or maintenance while alive shall be a minimum of 2 feet 6 inches (762 mm).”
7. An industrial worker is assessing an area where excessive combustible dusts may be present, such as an agricultural facility. How must the worker determine the classification of this area?
Answer: Each room, section, or area shall be considered individually in determining its classification. The regulation requires individual consideration of each room, section, or area to determine its specific hazardous classification.
29 CFR § 1910.307(a): “Each room, section or area shall be considered individually in determining its classification.”
8. Where must overcurrent devices be located to comply with safety requirements for accessibility and protection?
Answer: Readily accessible to each employee or authorized building management personnel. The regulation requires devices to be readily accessible to employees or authorized personnel and prohibits locations exposed to physical damage or near ignitable materials.
29 CFR § 1910.304(f): “Overcurrent devices shall be readily accessible to each employee or authorized building management personnel. These overcurrent devices may not be located where they will be exposed to physical damage or in the vicinity of easily ignitable material.”
9. An electrician is working on a switchboard that is 7 feet wide. The working space in front of the board is not doubled, and there is no continuous unobstructed way of exit travel. How many entrances are required for this switchboard?
Answer: One entrance at each end of the board. Since the board is wider than 6 feet and neither exception (unobstructed exit or doubled workspace) applies, an entrance is required at each end.
29 CFR § 1910.303(h): “On switchboard and control panels exceeding 1.83 m (6.0 ft) in width, there shall be one entrance at each end of such boards unless the location of the switchboards and control panels permits a continuous and unobstructed way of exit travel, or unless the work space required in paragraph (h)(5)(i) of this section is doubled.”
10. An electrician is installing the disconnecting means for runway contact conductors on a new overhead crane system. Which of the following is a mandatory requirement for the placement and operation of this disconnecting means?
Answer: It must be readily accessible and operable from the ground or floor level. The regulation requires the disconnecting means to be accessible and operable from the ground or floor level.
29 CFR § 1910.306(b): “The disconnecting means shall open all ungrounded conductors simultaneously and shall be: (i) Readily accessible and operable from the ground or floor level;”
11. A worker is inspecting bare terminals of transformers and motor controllers in a tunnel. What type of enclosure is required for these live parts?
Answer: Enclosures that are drip-proof, weatherproof, or submersible as required by environmental conditions. Because tunnels present specific environmental hazards, the regulation requires that enclosures for bare terminals be rated for those conditions (drip-proof, weatherproof, or submersible) rather than just standard indoor enclosures.
29 CFR § 1926.408(a): “Enclosures for use in tunnels shall be drip-proof, weatherproof, or submersible as required by the environmental conditions.”
12. An industrial worker is handling unsealed batteries in a charging area. What personal protective equipment (PPE) is required by the standard?
Answer: Face shields, aprons, and rubber gloves. The rule specifically lists face shields, aprons, and rubber gloves as the required PPE for workers handling batteries or acids.
29 CFR § 1926.441(a): “Face shields, aprons, and rubber gloves shall be provided for workers handling acids or batteries.”
13. An electrician is installing fixed lighting fixtures marked for use only in Class I, Division 2 locations. Which marking requirement is waived for this specific equipment?
Answer: The group marking. The rule states that these specific lighting fixtures do not need to be marked to indicate the group.
29 CFR § 1926.407(b): “Fixed lighting fixtures marked for use only in Class I, Division 2 locations need not be marked to indicate the group.”
14. An electrician is setting up an emergency lighting system for a facility. To ensure compliance, how must the system be arranged regarding individual lighting elements?
Answer: The failure of any individual lighting element cannot leave any space in total darkness. The regulation requires the emergency lighting system to be designed so that a single bulb failure does not result in total darkness in any area.
29 CFR § 1910.308(b): “Where emergency lighting is necessary, the system shall be so arranged that the failure of any individual lighting element, such as the burning out of a light bulb, cannot leave any space in total darkness.”
15. An electrician is inspecting a junction box where wires are routed through a raceway embedded in the wall finish. According to the definitions provided, how should these wires be classified?
Answer: Concealed. The rule states that wires in concealed raceways are considered concealed, even if they can be accessed by withdrawing them.
29 CFR § 1926.449: “Concealed. Rendered inaccessible by the structure or finish of the building. Wires in concealed raceways are considered concealed, even though they may become accessible by withdrawing them.”
16. A worker needs to run open conductors over a public street. What is the minimum vertical clearance from the ground required for these conductors?
Answer: 18 feet (5.49 m). Conductors running over public streets must maintain a minimum clearance of 18 feet from the ground.
29 CFR § 1926.404(c): “18 feet (5.49 m)—over public streets, alleys, roads, and driveways.”
17. An industrial worker is installing a self-supporting metal antenna structure outdoors. What is the primary safety requirement regarding its location relative to overhead electric light and power circuits?
Answer: It must be located as far away as necessary to prevent the antenna or structure from falling into or making accidental contact with circuits over 150 volts to ground. The rule focuses on preventing accidental contact or falling into circuits over 150 volts to ground, rather than a fixed distance for all voltages.
29 CFR § 1910.308(e): “Outdoor metal structures supporting antennas, as well as self-supporting antennas such as vertical rods or dipole structures, shall be located as far away from overhead conductors of electric light and power circuits of over 150 volts to ground as necessary to prevent the antenna or structure from falling into or making accidental contact with such circuits.”
18. An electrician is evaluating whether a specific wiring method is 'accessible' under OSHA definitions. Which condition must be met for the wiring to be classified as accessible?
Answer: The wiring must be capable of being removed or exposed without damaging the building structure or finish. Wiring is considered accessible if it can be exposed or removed without causing damage to the building's structure or finish, distinguishing it from concealed wiring.
29 CFR § 1910.399: “Accessible. (As applied to wiring methods.) Capable of being removed or exposed without damaging the building structure or finish, or not permanently closed in by the structure or finish of the building.”
19. An electrician is connecting the grounding electrode to the equipment grounding conductor at the service equipment. Which specific conductor is defined as performing this connection?
Answer: Grounding electrode conductor. The definition identifies the grounding electrode conductor as the component linking the grounding electrode to the equipment grounding or grounded conductors at the service.
29 CFR § 1910.399: “Grounding electrode conductor. The conductor used to connect the grounding electrode to the equipment grounding conductor, to the grounded conductor, or to both, of the circuits at the service equipment or at the source of a separately derived system.”
20. A worker is selecting a conduit type to hold wires in a wet location. Based on the definition of 'Raceway,' which of the following is listed as a type of raceway?
Answer: Liquidtight flexible metal conduit. Liquidtight flexible metal conduit is listed in the rule as a type of raceway, whereas the other options are not listed in this definition.
29 CFR § 1926.449: “Raceways may be of metal or insulating material, and the term includes rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquidtight flexible metal conduit, flexible metallic tubing, flexible metal conduit, electrical metallic tubing, underfloor raceways, cellular concrete floor raceways, cellular metal floor raceways, surface raceways, wireways, and busways.”
21. An electrician is installing a switch capable of making, carrying, and interrupting specified currents in a system operating over 600 volts, nominal. What is the specific term for this switch?
Answer: Interrupter switch. The rule defines an interrupter switch specifically for systems over 600 volts nominal that can make, carry, and interrupt specified currents.
29 CFR § 1926.449: “Interrupter switch. (Over 600 volts, nominal.) A switch capable of making, carrying, and interrupting specified currents.”
22. An electrician is inspecting a transformer vault. Which foreign element is prohibited from entering or passing through the vault?
Answer: Any pipe or duct system foreign to the electrical installation. The rule strictly forbids any pipe or duct system that is foreign to the electrical installation from entering the transformer vault.
29 CFR § 1910.305(j): “Any pipe or duct system foreign to the electrical installation may not enter or pass through a transformer vault.”
23. An unqualified employee is working in an area where they face a risk of electric shock not reduced to a safe level by installation requirements. What additional training obligation applies to this employee beyond standard safety-related work practices?
Answer: They must be trained in any electrically related safety practices not specifically addressed by the standard but which are necessary for their safety. The rule requires unqualified persons to be trained in additional safety practices necessary for their safety that are not covered by the specific sections listed.
29 CFR § 1910.332(b): “Employees who are covered by paragraph (a) of this section but who are not qualified persons shall also be trained in and familiar with any electrically related safety practices not specifically addressed by §§ 1910.331 through 1910.335 but which are necessary for their safety.”
24. An electrician is installing a Class 1 power-limited circuit. What are the maximum rated output limits for the source supplying this circuit?
Answer: Not more than 30 volts and 1000 volt-amperes. The rule strictly defines a Class 1 power-limited circuit source as having a maximum output of 30 volts and 1000 volt-amperes.
29 CFR § 1910.308(c): “A Class 1 power-limited circuit shall be supplied from a source having a rated output of not more than 30 volts and 1000 volt-amperes.”
25. An industrial worker is evaluating whether a specific piece of equipment requires guarding because it is 'Exposed.' Which scenario fits the definition of exposed live parts?
Answer: The parts are capable of being inadvertently touched or approached nearer than a safe distance by a person and are not suitably guarded, isolated, or insulated. Live parts are considered exposed if they are not guarded, isolated, or insulated, allowing a person to inadvertently touch them or get too close.
29 CFR § 1910.399: “Exposed. (As applied to live parts.) Capable of being inadvertently touched or approached nearer than a safe distance by a person. It is applied to parts not suitably guarded, isolated, or insulated.”