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

What is the total capacitance of three 100 picofarad capacitors connected in series?

Answer: 33.3 pF

For equal capacitors in series, total capacitance equals one capacitor's value divided by the number of capacitors: 100/3 ≈ 33.3 pF.

What is the time constant of a circuit consisting of a 100 microhenry inductor in series with a 50 ohm resistor?

Answer: 2 microseconds

The time constant τ = L/R = 100×10⁻⁶/50 = 2×10⁻⁶ seconds, or 2 microseconds.

In a transmission line, what does a standing wave ratio (SWR) of 1:1 indicate?

Answer: A perfectly matched load with no reflected power

An SWR of 1:1 means the load impedance perfectly matches the characteristic impedance of the transmission line, resulting in zero reflected power.

What is the characteristic impedance of a lossless transmission line with a distributed inductance of 250 nanohenries per meter and a distributed capacitance of 100 picofarads per meter?

Answer: 50 ohms

Z₀ = √(L/C) = √(250×10⁻⁹/100×10⁻¹²) = √2500 = 50 ohms.

What is the effect of mutual coupling between two inductors wound on the same core?

Answer: The total inductance can be greater or less than the sum depending on winding direction

When inductors share a core, mutual inductance either adds to or subtracts from the total depending on whether the magnetic fields aid or oppose each other.

What is the relationship between peak voltage and RMS voltage in a pure sine wave?

Answer: RMS voltage equals peak voltage divided by the square root of 2

For a sine wave, Vrms = Vpeak / √2, which is approximately 0.707 times the peak voltage.