FREE HAM Radio Extra Class Test Advanced Electrical Principles Questions and Answers Flashcards

What is the resonant frequency of a series RLC circuit with an inductance of 10 microhenries and a capacitance of 100 picofarads?

Answer: 5.03 MHz

Using f = 1/(2π√(LC)), with L = 10 µH and C = 100 pF, the resonant frequency calculates to approximately 5.03 MHz.

In a circuit operating at 14 MHz, what is the reactance of a 300 picofarad capacitor?

Answer: 37.9 ohms

Capacitive reactance Xc = 1/(2πfC) = 1/(2π × 14×10⁶ × 300×10⁻¹²) ≈ 37.9 ohms.

What happens to the impedance of a parallel resonant circuit at the resonant frequency?

Answer: Impedance reaches its maximum value

At resonance, a parallel RLC circuit exhibits maximum impedance because the inductive and capacitive branch currents cancel each other.

What is the skin effect in a conductor at RF frequencies?

Answer: Current tends to flow near the surface of the conductor

At RF frequencies, alternating current concentrates near the outer surface of a conductor due to electromagnetic induction, increasing effective resistance.

What is the power factor of a circuit with a phase angle of 45 degrees between voltage and current?

Answer: 0.707

Power factor equals the cosine of the phase angle, so cos(45°) = 0.707.

What is the Q factor of a series RLC circuit with a resistance of 5 ohms, an inductance of 10 microhenries at a resonant frequency of 7.1 MHz?

Answer: 89.2

Q = (2πfL)/R = (2π × 7.1×10⁶ × 10×10⁻⁶)/5 ≈ 89.2.