CBET General Practice 4 — Questions and Answers
Question 1: A hospital's isolated power system (IPS) is designed primarily to protect against:
- Power surges from the utility grid
- Macroshock from single-fault ground currents in wet locations (Correct answer)
- Electromagnetic interference from adjacent equipment
- Overloading of the facility's main circuit breakers
Correct answer: Macroshock from single-fault ground currents in wet locations
An IPS isolates the patient care circuit from ground so a single fault does not create a complete circuit for dangerous ground currents (macroshock).
Question 2: When testing a line isolation monitor (LIM), the alarm should activate when the hazard current exceeds:
- 1 mA
- 2 mA
- 5 mA (Correct answer)
- 10 mA
Correct answer: 5 mA
NFPA 99 requires the LIM alarm to activate when total hazard current reaches 5 mA, indicating the IPS isolation has degraded to a dangerous level.
Question 3: A technician notices the hospital's oxygen wall outlet delivers flow but at a lower pressure than specification. The MOST likely cause is:
- Contamination of the oxygen supply with nitrogen
- A partially closed or faulty zone valve upstream
- A calibration error in the flowmeter
- Excessive demand from too many simultaneous users on that zone (Correct answer)
Correct answer: Excessive demand from too many simultaneous users on that zone
Excessive simultaneous demand on a piped medical gas zone creates a pressure drop due to flow resistance in the supply piping.
Question 4: In a digital-to-analog converter (DAC) used in medical equipment, increasing the bit resolution from 8-bit to 12-bit:
- Doubles the output voltage range
- Increases the number of discrete output levels from 256 to 4,096 (Correct answer)
- Reduces conversion speed by a factor of 4
- Decreases the signal-to-noise ratio
Correct answer: Increases the number of discrete output levels from 256 to 4,096
An 8-bit DAC produces 2^8 = 256 levels while a 12-bit DAC produces 2^12 = 4,096 levels, providing finer output resolution.
Question 5: A technician is performing annual PM on a hospital bed. Which safety check is MOST critical for patient fall prevention?
- Verifying the bed's Trendelenburg angle accuracy
- Testing siderail locking mechanisms for secure engagement (Correct answer)
- Calibrating the bed's weight scale
- Inspecting the mattress cover for tears
Correct answer: Testing siderail locking mechanisms for secure engagement
Siderail locking mechanism failure is directly linked to patient falls, making it the highest-priority safety check during hospital bed PM.
Question 6: The International System of Units (SI) base unit for electric current is the:
- Volt
- Watt
- Ampere (Correct answer)
- Coulomb
Correct answer: Ampere
The ampere (A) is the SI base unit for electric current, defined as the flow of electric charge past a point per unit time.
Question 7: A biomedical technician must ensure an ECG machine's patient lead leakage current does not exceed which limit for a CF-type device per IEC 60601-1?
- 100 µA under normal conditions
- 10 µA under normal conditions (Correct answer)
- 50 µA under normal conditions
- 500 µA under normal conditions
Correct answer: 10 µA under normal conditions
For CF (cardiac floating) applied parts, IEC 60601-1 limits patient leakage current to 10 µA under normal conditions due to direct cardiac risk.
CBET General Practice 4
A hospital's isolated power system (IPS) is designed primarily to protect against: