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 characteristic impedance of a coaxial cable primarily determined by?
Answer: The ratio of outer to inner conductor diameters and the dielectric constant
Characteristic impedance of coax is determined by Z0 = (138/√εr) × log(D/d), where D and d are outer and inner conductor diameters and εr is the dielectric constant.
What phenomenon occurs when a signal in one conductor induces a signal in an adjacent conductor?
Answer: Crosstalk (electromagnetic coupling)
Crosstalk is the undesired inductive or capacitive coupling of a signal from one conductor into an adjacent conductor.
In a phase-locked loop (PLL), what is the function of the voltage-controlled oscillator (VCO)?
Answer: Generate an output frequency proportional to input voltage
The VCO generates an output frequency that is proportional to its input control voltage, forming the core of the PLL feedback system.
What is the purpose of a ferrite bead on a cable or PCB trace?
Answer: Suppress high-frequency RF noise and EMI
A ferrite bead acts as a frequency-dependent resistor that absorbs and dissipates high-frequency RF energy, suppressing EMI.
When measuring AC voltage with a true-RMS meter, what value is displayed for a 170V peak sine wave?
Answer: 120V
RMS voltage of a sine wave = Vpeak / √2 = 170 / 1.414 ≈ 120V, which is the effective heating value equivalent to that DC voltage.
What is the primary advantage of using a differential amplifier in broadcast audio equipment?
Answer: Rejection of common-mode noise on balanced lines
A differential amplifier rejects signals common to both inputs (common-mode noise) while amplifying the difference signal, making it ideal for balanced audio connections.
In digital logic, what is the purpose of a Schmitt trigger input?
Answer: To provide hysteresis and prevent false triggering from noisy signals
A Schmitt trigger uses hysteresis (different threshold voltages for rising and falling edges) to cleanly convert slow or noisy signals into crisp digital transitions.