CBET Electronics and Electrical Safety 4 — Questions and Answers
Question 1: What is the maximum allowable chassis leakage current for a patient-connected device in a general care area according to NFPA 99?
- 100 µA (Correct answer)
- 500 µA
- 10 µA
- 300 µA
Correct answer: 100 µA
NFPA 99 limits chassis leakage current to 100 µA for patient-connected equipment in general care areas.
Question 2: A Zener diode is primarily used in electronic circuits to:
- Amplify small signals
- Regulate voltage (Correct answer)
- Rectify AC to DC
- Filter high-frequency noise
Correct answer: Regulate voltage
Zener diodes operate in reverse breakdown to maintain a stable reference voltage, making them ideal for voltage regulation.
Question 3: Which type of transformer configuration is used in medical-grade isolated power systems to prevent shock hazard?
- Autotransformer
- Step-down transformer
- Isolation transformer (Correct answer)
- Toroidal transformer
Correct answer: Isolation transformer
Isolation transformers break the galvanic connection between utility power and the patient care area, preventing ground-fault shock.
Question 4: In a series RLC circuit at resonance, the impedance is:
- Maximum and purely resistive
- Zero
- Equal to inductive reactance only
- Minimum and purely resistive (Correct answer)
Correct answer: Minimum and purely resistive
At resonance, XL and XC cancel each other, leaving only resistance, so impedance is at its minimum and purely resistive.
Question 5: What does the term 'macroshock' refer to in electrical safety?
- Current applied directly to the heart via a catheter
- Large current entering the body through the skin (Correct answer)
- Electrostatic discharge from equipment surfaces
- Current leakage below 10 µA
Correct answer: Large current entering the body through the skin
Macroshock involves relatively large currents (milliamps) applied externally to the body, typically causing ventricular fibrillation at 100 mA.
Question 6: A hospital-grade receptacle differs from a standard commercial receptacle primarily by:
- Higher voltage rating
- Green dot marking and reinforced contacts (Correct answer)
- Three-phase wiring capability
- Built-in GFCI protection
Correct answer: Green dot marking and reinforced contacts
Hospital-grade receptacles are identified by a green dot and feature stronger contacts and construction to withstand repeated plug insertions.
Question 7: Which logic gate outputs HIGH only when all inputs are HIGH?
- OR gate
- NAND gate
- AND gate (Correct answer)
- NOR gate
Correct answer: AND gate
An AND gate produces a HIGH output only when every input is simultaneously HIGH.
CBET Electronics and Electrical Safety 4
What is the maximum allowable chassis leakage current for a patient-connected device in a general care area according to NFPA 99?