Electronic & Electrical Fundamentals Flashcards
7 cards from real CBT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electronic & Electrical Fundamentals flashcards as text
What is the function of a varactor diode in a circuit?
Answer: Act as a voltage-controlled capacitor
A varactor (varicap) diode exploits the voltage-dependent capacitance of a reverse-biased pn junction to act as a voltage-controlled capacitor.
In a three-phase power system, if the line voltage is 208V, what is the phase voltage?
Answer: 120V
Phase voltage = Line voltage / √3 = 208 / 1.732 ≈ 120V in a wye-connected three-phase system.
What type of noise is caused by the random movement of electrons due to thermal energy and is proportional to temperature?
Answer: Johnson-Nyquist (thermal) noise
Johnson-Nyquist noise (thermal noise) is generated by random thermal motion of electrons and increases with absolute temperature.
What does VSWR stand for in transmission line theory?
Answer: Voltage Standing Wave Ratio
VSWR (Voltage Standing Wave Ratio) describes the ratio of maximum to minimum voltage on a transmission line due to reflected waves from an impedance mismatch.
Which logic gate produces a HIGH output only when all inputs are HIGH?
Answer: AND gate
An AND gate outputs HIGH (logic 1) only when all of its inputs are simultaneously HIGH.
What is the -3dB frequency of a low-pass RC filter with R=1kΩ and C=0.1μF?
Answer: 1592 Hz
The cutoff frequency fc = 1/(2πRC) = 1/(2π × 1000 × 0.0000001) ≈ 1592 Hz.
In a switching power supply, what component is primarily responsible for energy storage and transfer between input and output?
Answer: Transformer or inductor
In switching power supplies, the transformer (isolated) or inductor (non-isolated) stores and transfers energy between the switching cycles.