CABT Healthcare and Electrical Safety 4 — Questions and Answers
Question 1: A GFCI (Ground Fault Circuit Interrupter) trips when it detects a current imbalance greater than:
- 1 mA
- 4–6 mA (Correct answer)
- 15 mA
- 30 mA
Correct answer: 4–6 mA
A GFCI monitors the difference between hot and neutral currents and trips when the imbalance exceeds approximately 4–6 mA, indicating ground fault current.
Question 2: In the context of electrical safety, 'macroshock' is defined as current entering the body:
- Directly into the heart via a catheter
- Through the intact skin surface (Correct answer)
- Through a broken ground conductor
- Via inductive coupling only
Correct answer: Through the intact skin surface
Macroshock refers to electric current entering and exiting through the skin surface, requiring higher currents (mA range) to cause fibrillation.
Question 3: Which color is used in the US to identify the grounding conductor in a standard electrical cord?
- White
- Black
- Green or bare copper (Correct answer)
- Red
Correct answer: Green or bare copper
In the United States, the protective ground conductor is identified by green insulation or left as bare copper wire.
Question 4: When testing total patient leakage current on an ECG monitor connected to a patient simulator, the technician should measure:
- Voltage across the chassis to ground
- Current from all patient-applied parts to ground collectively (Correct answer)
- Resistance of the power cord
- DC offset of the signal amplifier
Correct answer: Current from all patient-applied parts to ground collectively
Total patient leakage current is measured by summing the current from all applied parts (leads) to ground under worst-case conditions.
Question 5: Under NFPA 99, receptacles in a Category 1 (critical care) patient care area must be:
- Standard duplex GFCI protected only
- Hospital-grade and connected to the equipment grounding system (Correct answer)
- Twist-lock to prevent accidental disconnection
- Color-coded blue for identification purposes
Correct answer: Hospital-grade and connected to the equipment grounding system
NFPA 99 requires hospital-grade receptacles in Category 1 areas to ensure reliable grounding and mechanical integrity under clinical conditions.
Question 6: The primary reason medical equipment in wet procedure areas must use an isolated power system is:
- To prevent electromagnetic interference with imaging equipment
- To ensure a single ground fault does not complete a circuit through a patient in a wet environment (Correct answer)
- To reduce energy consumption during surgical procedures
- To comply with fire suppression system requirements
Correct answer: To ensure a single ground fault does not complete a circuit through a patient in a wet environment
Wet environments lower skin resistance dramatically; an isolated power system prevents the first ground fault from producing a shock through the patient.
Question 7: Which biomedical safety test verifies that all conductive surfaces within a patient care vicinity are bonded to a common reference potential?
- Dielectric withstand test
- Equipotential bonding test (Correct answer)
- Patient lead isolation test
- Hipot test
Correct answer: Equipotential bonding test
The equipotential bonding test measures resistance between exposed conductive surfaces to confirm they share the same ground reference, preventing potential differences.
CABT Healthcare and Electrical Safety 4
A GFCI (Ground Fault Circuit Interrupter) trips when it detects a current imbalance greater than: