ASP Electrical Safety 4 — Questions and Answers
Question 1: What is the minimum approach distance (MAD) concept used for in electrical safety?
- Determining how far a worker must stay from energized conductors based on voltage level (Correct answer)
- Setting the maximum length of extension cords permitted on a job site
- Establishing the required distance between electrical panels and fire extinguishers
- Defining the spacing between circuit breakers in a panelboard
Correct answer: Determining how far a worker must stay from energized conductors based on voltage level
Minimum approach distance is the closest distance a qualified worker may approach energized conductors or circuit parts, determined by the system voltage and overvoltage category.
Question 2: Which OSHA standard primarily governs electrical safety in general industry workplaces?
- 29 CFR 1910.147
- 29 CFR 1910.303–1910.399 (Subpart S) (Correct answer)
- 29 CFR 1926.416
- 29 CFR 1910.132
Correct answer: 29 CFR 1910.303–1910.399 (Subpart S)
OSHA 29 CFR 1910 Subpart S (sections 303–399) covers electrical safety standards for general industry workplaces.
Question 3: What does an equipotential bonding system accomplish in electrical safety?
- It increases current capacity of conductors
- It ensures all conductive parts are at the same electrical potential to eliminate shock hazard (Correct answer)
- It provides a path for fault current to flow to the load
- It isolates high-voltage equipment from low-voltage systems
Correct answer: It ensures all conductive parts are at the same electrical potential to eliminate shock hazard
Equipotential bonding connects all conductive parts together so no voltage difference exists between them, eliminating the risk of electric shock from step or touch potential.
Question 4: A worker contacts an energized conductor and cannot let go due to muscle tetany. What physiological phenomenon causes this?
- The body's natural grounding response
- Sustained muscle contraction caused by alternating current stimulating motor nerves at 60 Hz (Correct answer)
- Ventricular fibrillation affecting motor neurons
- Thermal burns to tendons causing mechanical contraction
Correct answer: Sustained muscle contraction caused by alternating current stimulating motor nerves at 60 Hz
60 Hz AC causes repeated stimulation of motor nerves, producing sustained involuntary muscle contraction (tetany) that prevents the victim from releasing the conductor.
Question 5: What is the purpose of a ground fault circuit interrupter (GFCI) compared to a standard circuit breaker?
- GFCI protects equipment from overloads; breakers protect people from shock
- GFCI detects small current imbalances (as low as 4–6 mA) and trips to protect against shock; breakers protect against overloads and short circuits (Correct answer)
- GFCI provides surge protection; breakers provide ground fault protection
- GFCI is rated for higher voltages than standard breakers
Correct answer: GFCI detects small current imbalances (as low as 4–6 mA) and trips to protect against shock; breakers protect against overloads and short circuits
GFCIs monitor the difference between hot and neutral current and trip within milliseconds when as little as 4–6 mA is detected flowing through an unintended path, protecting against electrocution.
Question 6: Under NFPA 70E, an 'electrically safe work condition' requires which sequence of steps?
- De-energize, verify absence of voltage, apply locks and tags, then test for absence of stored energy (Correct answer)
- Apply PPE, de-energize, verify with a voltmeter, then begin work
- Identify the circuit, apply warning tags, test voltage, then de-energize
- Lock out the main breaker, post a safety sign, and notify supervision
Correct answer: De-energize, verify absence of voltage, apply locks and tags, then test for absence of stored energy
NFPA 70E requires de-energizing, isolating, locking out/tagging out, releasing stored energy, and verifying absence of voltage before work begins.
Question 7: Which factor most significantly determines the severity of an electric shock injury?
- The color of the insulation on the wire
- The magnitude of current flowing through the body and the path it takes (Correct answer)
- The ambient temperature of the work environment
- The brand of PPE worn by the worker
Correct answer: The magnitude of current flowing through the body and the path it takes
Severity of electrical injury depends primarily on current magnitude (in milliamps) and the path through the body, particularly whether it passes through the heart.
ASP Electrical Safety 4
What is the minimum approach distance (MAD) concept used for in electrical safety?