CBET Basic 3 ā Questions and Answers
Question 1: Which law states that the algebraic sum of all currents entering and leaving a node equals zero?
- Ohm's Law
- Faraday's Law
- Kirchhoff's Current Law (Correct answer)
- Thevenin's Theorem
Correct answer: Kirchhoff's Current Law
Kirchhoff's Current Law (KCL) is based on conservation of charge: all current entering a junction must equal all current leaving it.
Question 2: What is the purpose of a Zener diode in a circuit?
- Amplify AC signals
- Regulate voltage by allowing reverse breakdown at a fixed voltage (Correct answer)
- Convert AC to DC
- Store electrical charge
Correct answer: Regulate voltage by allowing reverse breakdown at a fixed voltage
A Zener diode operates in reverse breakdown at a stable, predictable voltage, making it ideal for voltage regulation.
Question 3: In biomedical equipment, which frequency range is used by most diathermy units?
- 0ā100 Hz
- 1ā10 kHz
- 300 kHz ā 5 MHz (Correct answer)
- 500 MHz ā 2 GHz
Correct answer: 300 kHz ā 5 MHz
Surgical diathermy (electrosurgical units) operates in the radiofrequency range of approximately 300 kHz to 5 MHz to cut and coagulate tissue without nerve stimulation.
Question 4: Which mathematical relationship describes exponential decay in an RC circuit?
- V(t) = Vā Ć e^(t/RC)
- V(t) = Vā Ć (1 - e^(-t/RC))
- V(t) = Vā Ć e^(-t/RC) (Correct answer)
- V(t) = Vā / (1 + RC)
Correct answer: V(t) = Vā Ć e^(-t/RC)
Voltage across a discharging capacitor decays exponentially as V(t) = Vā Ć e^(-t/RC), where RC is the time constant.
Question 5: What is the function of an op-amp configured in a non-inverting amplifier topology?
- Inverts and attenuates the input signal
- Amplifies the input signal with positive gain and no phase inversion (Correct answer)
- Acts as an oscillator to generate waveforms
- Provides impedance matching only, with unity gain
Correct answer: Amplifies the input signal with positive gain and no phase inversion
A non-inverting op-amp configuration amplifies the input signal with gain = 1 + (Rf/Rin) and maintains the same phase as the input.
Question 6: What is the meaning of 'Type CF' applied part classification according to IEC 60601-1?
- Defibrillation-proof applied part for chest use
- Applied part not intended for direct cardiac contact with basic isolation
- Floating applied part suitable for direct cardiac contact, defibrillation-proof (Correct answer)
- Applied part for external use only with no patient contact
Correct answer: Floating applied part suitable for direct cardiac contact, defibrillation-proof
Type CF applied parts have the strictest leakage current limits and are defibrillation-proof, making them safe for direct cardiac application.
Question 7: Which gas law states that pressure and volume are inversely proportional at constant temperature?
- Charles's Law
- Gay-Lussac's Law
- Boyle's Law (Correct answer)
- Dalton's Law
Correct answer: Boyle's Law
Boyle's Law (PāVā = PāVā) describes the inverse relationship between pressure and volume of a gas at constant temperature.
CBET Basic 3
Which law states that the algebraic sum of all currents entering and leaving a node equals zero?