ASVAB ASVAB Electronics Fundamentals and Circuits 5 — Questions and Answers
Question 1: A circuit has a 10Ω resistor and a 10Ω inductive reactance connected in series. What is the impedance?
- 20Ω
- 5Ω
- 14.14Ω (Correct answer)
- 100Ω
Correct answer: 14.14Ω
Impedance Z = √(R² + XL²) = √(100 + 100) = √200 ≈ 14.14Ω.
Question 2: What happens to the resonant frequency of an LC circuit if the inductance is increased fourfold while capacitance stays the same?
- It doubles
- It is halved (Correct answer)
- It quadruples
- It stays the same
Correct answer: It is halved
Resonant frequency f = 1/(2π√LC); quadrupling L makes √(4L) = 2√L, so frequency is halved.
Question 3: Which semiconductor device is commonly used as a voltage-controlled switch in digital logic circuits?
- BJT in common-emitter mode
- MOSFET (Correct answer)
- Schottky diode
- UJT
Correct answer: MOSFET
MOSFETs are the dominant switching device in digital logic because they are voltage-controlled and have very high input impedance.
Question 4: What is the purpose of a bypass capacitor placed across a power supply rail in an amplifier circuit?
- Increase the DC gain of the amplifier
- Filter out AC ripple and high-frequency noise from the supply voltage (Correct answer)
- Block DC from reaching the output
- Set the operating frequency of the amplifier
Correct answer: Filter out AC ripple and high-frequency noise from the supply voltage
Bypass capacitors provide a low-impedance path to ground for AC noise on the DC supply rail, keeping the supply clean.
Question 5: A 120V RMS AC source is applied across a circuit. What is the approximate peak voltage?
- 120V
- 85V
- 170V (Correct answer)
- 240V
Correct answer: 170V
Peak voltage = RMS × √2 ≈ 120 × 1.414 ≈ 170V.
Question 6: In a common-emitter BJT amplifier, what effect does increasing the collector resistor (RC) have on voltage gain?
- Voltage gain decreases
- Voltage gain increases (Correct answer)
- Voltage gain is unaffected
- The transistor saturates immediately
Correct answer: Voltage gain increases
Voltage gain Av ≈ RC/re, so increasing RC directly increases the voltage gain of the stage.
Question 7: Which type of filter passes low frequencies and blocks high frequencies?
- Band-pass filter
- High-pass filter
- Low-pass filter (Correct answer)
- Band-stop filter
Correct answer: Low-pass filter
A low-pass filter allows signals below its cutoff frequency to pass while attenuating signals above that frequency.
ASVAB ASVAB Electronics Fundamentals and Circuits 5
A circuit has a 10Ω resistor and a 10Ω inductive reactance connected in series.
What is the impedance?