ASVAB Electronics Fundamentals and Circuits Flashcards

A circuit has a 10Ω resistor and a 10Ω inductive reactance connected in series. What is the impedance?

Answer: 14.14Ω

Impedance Z = √(R² + XL²) = √(100 + 100) = √200 ≈ 14.14Ω.

What happens to the resonant frequency of an LC circuit if the inductance is increased fourfold while capacitance stays the same?

Answer: It is halved

Resonant frequency f = 1/(2π√LC); quadrupling L makes √(4L) = 2√L, so frequency is halved.

Which semiconductor device is commonly used as a voltage-controlled switch in digital logic circuits?

Answer: MOSFET

MOSFETs are the dominant switching device in digital logic because they are voltage-controlled and have very high input impedance.

What is the purpose of a bypass capacitor placed across a power supply rail in an amplifier circuit?

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.

A 120V RMS AC source is applied across a circuit. What is the approximate peak voltage?

Answer: 170V

Peak voltage = RMS × √2 ≈ 120 × 1.414 ≈ 170V.

In a common-emitter BJT amplifier, what effect does increasing the collector resistor (RC) have on voltage gain?

Answer: Voltage gain increases

Voltage gain Av ≈ RC/re, so increasing RC directly increases the voltage gain of the stage.

Which type of filter passes low frequencies and blocks high frequencies?

Answer: Low-pass filter

A low-pass filter allows signals below its cutoff frequency to pass while attenuating signals above that frequency.