CBET Basic 4 â Questions and Answers
Question 1: What does the term 'impedance' represent in an AC circuit?
- Only the resistive opposition to current flow
- The total opposition to AC current including resistance, inductance, and capacitance (Correct answer)
- The ratio of inductance to capacitance
- The phase difference between voltage and current
Correct answer: The total opposition to AC current including resistance, inductance, and capacitance
Impedance (Z) is the total opposition to AC current flow, combining resistance (R) with reactance (X) from inductors and capacitors.
Question 2: In a hospital power system, what color is the equipment grounding conductor per NEC standards?
- White or gray
- Black
- Green or bare (Correct answer)
- Red
Correct answer: Green or bare
Per NEC Article 250, equipment grounding conductors are identified by green insulation, green with yellow stripe, or bare copper.
Question 3: Which physiological signal has the lowest typical amplitude among the following?
- ECG (electrocardiogram)
- EEG (electroencephalogram) (Correct answer)
- EMG (electromyogram)
- EOG (electrooculogram)
Correct answer: EEG (electroencephalogram)
EEG signals are typically in the range of 2â200 ΞV, which is lower than ECG (~1 mV), EMG (~1â10 mV), and EOG (~100 ΞVâ1 mV).
Question 4: What is the half-value layer (HVL) in radiological physics?
- The depth at which radiation intensity doubles
- The thickness of material needed to reduce radiation intensity by half (Correct answer)
- The energy at which photons are most absorbed
- The maximum safe exposure dose per year
Correct answer: The thickness of material needed to reduce radiation intensity by half
The HVL is the thickness of a specified material that reduces the intensity of ionizing radiation to one-half of its original value.
Question 5: Which component is used to measure very small DC currents in biomedical instruments by converting them to a voltage?
- Wheatstone bridge
- Transimpedance amplifier (current-to-voltage converter) (Correct answer)
- Differential amplifier
- Sample-and-hold circuit
Correct answer: Transimpedance amplifier (current-to-voltage converter)
A transimpedance amplifier uses an op-amp with a feedback resistor to convert input current to an output voltage proportional to that current.
Question 6: What does CMRR measure in a differential amplifier?
- The bandwidth of the amplifier at 3 dB down
- The ability to reject signals common to both inputs while amplifying the difference (Correct answer)
- The ratio of output noise to input signal
- The maximum supply voltage the amplifier can tolerate
Correct answer: The ability to reject signals common to both inputs while amplifying the difference
Common-Mode Rejection Ratio (CMRR) quantifies how well an amplifier rejects noise or interference that appears equally on both inputs.
Question 7: When performing preventive maintenance on an infusion pump, which test verifies the accuracy of fluid delivery rate?
- Dielectric strength test
- Gravimetric flow rate test (Correct answer)
- Hipot test
- Ground bond resistance test
Correct answer: Gravimetric flow rate test
A gravimetric test weighs the fluid delivered over a set time period to calculate actual flow rate and compare it against the programmed rate.
CBET Basic 4
What does the term 'impedance' represent in an AC circuit?