OSHA 10-Hour Construction ReviewFocus Four HazardsHard
A worker is using a portable electric drill on a construction site. The drill's power cord has a broken ground prong. What is the most significant electrocution hazard associated with using this tool in its current condition?
- AThe circuit breaker will trip immediately upon plugging in the tool.
- BThe tool will not operate correctly due to insufficient power.
- CThe drill will draw excessive current, causing it to overheat.
- DA fault could energize the metal casing, creating a shock hazard.
Show answer & explanationAnswer & explanation
Correct answer: D. A fault could energize the metal casing, creating a shock hazard.
A broken ground prong eliminates the safety path for fault current. If an internal electrical fault occurs, the metal casing of the drill can become energized, posing a severe shock or electrocution risk to the user.
Why the other options are wrong
- A. A circuit breaker trips on overcurrent or short circuit, not simply a missing ground, unless a fault occurs simultaneously.
- B. The tool can still operate without a ground, but without the safety benefits of proper grounding.
- C. While overheating is a risk with electrical tools, a broken ground prong specifically facilitates shock, not necessarily excessive current draw.
Tool Grounding Safety
Grounding provides a safe path for fault current to flow to the earth, preventing electrical shock by ensuring that exposed metal parts of an electrical tool do not become energized.
- Protects against electrocution.
- Requires a continuous path to ground.
- Broken ground prongs or faulty wiring defeat grounding.
Memory trick: Grounding's friend, shock's end.