HAM HAM Radio Extra Class Test Practical Electronics Circuits Questions and Answers 2 — Questions and Answers
Question 1: What is the primary purpose of a bleeder resistor in a power supply circuit?
- To discharge filter capacitors when the supply is turned off (Correct answer)
- To increase the output voltage under load
- To regulate the current flowing to the load
- To filter out AC ripple from the DC output
Correct answer: To discharge filter capacitors when the supply is turned off
A bleeder resistor safely discharges stored energy in filter capacitors after the power supply is switched off, preventing electrical shock.
Question 2: In a Class AB amplifier, what advantage does it offer over a Class B amplifier?
- Reduced crossover distortion (Correct answer)
- Higher power efficiency
- Greater voltage gain
- Lower component count
Correct answer: Reduced crossover distortion
Class AB biases both transistors slightly into conduction, eliminating the dead zone at the crossover point that causes distortion in Class B designs.
Question 3: What is the function of a bypass capacitor placed across the emitter resistor in a common-emitter amplifier?
- To increase AC voltage gain by shorting the emitter resistor at signal frequencies (Correct answer)
- To stabilize the DC bias point of the transistor
- To filter out power supply noise from the circuit
- To prevent thermal runaway of the transistor
Correct answer: To increase AC voltage gain by shorting the emitter resistor at signal frequencies
The bypass capacitor provides a low-impedance path for AC signals around the emitter resistor, removing the negative feedback that reduces gain at signal frequencies.
Question 4: Which component in a voltage regulator circuit provides the reference voltage for comparison?
- A zener diode (Correct answer)
- A coupling capacitor
- An RF choke
- A varactor diode
Correct answer: A zener diode
A zener diode maintains a stable reference voltage across its terminals when reverse-biased, which the regulator compares against the output to maintain regulation.
Question 5: What happens to the Q factor of a parallel resonant circuit if the resistance in the circuit increases?
- The Q factor decreases (Correct answer)
- The Q factor increases
- The Q factor remains unchanged
- The resonant frequency shifts higher
Correct answer: The Q factor decreases
Q factor equals the ratio of reactive power to resistive power, so increasing resistance raises losses and reduces the circuit's Q factor.
Question 6: What type of filter topology uses both series inductors and shunt capacitors to achieve a sharp cutoff response?
- A pi-network low-pass filter (Correct answer)
- A simple RC high-pass filter
- A single-pole Butterworth filter
- A resistive T-network attenuator
Correct answer: A pi-network low-pass filter
A pi-network filter uses a capacitor-inductor-capacitor arrangement that provides steeper rolloff than simple RC filters due to multiple reactive elements.
HAM HAM Radio Extra Class Test Practical Electronics Circuits Questions and Answers 2
What is the primary purpose of a bleeder resistor in a power supply circuit?