CBT Electronic & Electrical Fundamentals 2 — Questions and Answers
Question 1: What is the impedance of a series RLC circuit at resonance?
- Equal to the inductive reactance
- Equal to the capacitive reactance
- Equal to the resistance only (Correct answer)
- Zero
Correct answer: Equal to the resistance only
At resonance, inductive and capacitive reactances cancel, leaving only the resistance as the circuit impedance.
Question 2: A transformer has a primary winding of 500 turns and a secondary of 100 turns. If the primary voltage is 120V, what is the secondary voltage?
- 600V
- 24V (Correct answer)
- 12V
- 240V
Correct answer: 24V
Using the turns ratio formula: Vs = Vp × (Ns/Np) = 120 × (100/500) = 24V.
Question 3: Which semiconductor device is typically used as a voltage regulator in simple circuits?
- BJT transistor
- Zener diode (Correct answer)
- Schottky diode
- PIN diode
Correct answer: Zener diode
A Zener diode maintains a nearly constant voltage across its terminals when reverse-biased beyond its breakdown voltage.
Question 4: In a parallel RC circuit, what happens to total impedance as frequency increases?
- Impedance increases
- Impedance decreases (Correct answer)
- Impedance remains constant
- Impedance becomes purely resistive
Correct answer: Impedance decreases
As frequency rises, capacitive reactance decreases, reducing the overall parallel impedance of the RC circuit.
Question 5: What is the primary function of a bypass capacitor in an amplifier circuit?
- Increase DC gain
- Block DC while passing AC signals to ground (Correct answer)
- Regulate supply voltage
- Filter RF interference from the input
Correct answer: Block DC while passing AC signals to ground
A bypass capacitor shorts AC signals to ground at a specific frequency, effectively removing the emitter resistor from the AC signal path to increase gain.
Question 6: Which law states that the algebraic sum of currents at any node in a circuit equals zero?
- Ohm's Law
- Faraday's Law
- Kirchhoff's Current Law (Correct answer)
- Kirchhoff's Voltage Law
Correct answer: Kirchhoff's Current Law
Kirchhoff's Current Law (KCL) states that the sum of currents entering a node equals the sum of currents leaving it.
Question 7: What type of filter passes frequencies below a cutoff frequency and attenuates those above it?
- High-pass filter
- Band-pass filter
- Low-pass filter (Correct answer)
- Notch filter
Correct answer: Low-pass filter
A low-pass filter allows signals with frequencies lower than the cutoff frequency to pass while attenuating higher frequencies.
CBT Electronic & Electrical Fundamentals 2
What is the impedance of a series RLC circuit at resonance?