BEE DC and AC Circuit Analysis 5

Question 1

What is the bandwidth of a series RLC resonant circuit with f₀ = 1000 Hz and Q = 50?

Accepted Answer

20 Hz

Answer

Bandwidth BW = f₀/Q = 1000/50 = 20 Hz, representing the range of frequencies within 3 dB of the resonant peak.

Question 2

In an AC circuit, the complex power S is defined as:

Accepted Answer

S = V × I* (voltage times conjugate of current)

Answer

Complex power S = V_rms × I*_rms gives the full power triangle: S = P + jQ, where P is real power and Q is reactive power.

Question 3

When analyzing a circuit using Norton's theorem, what is the Norton current (IN)?

Accepted Answer

The short-circuit current at the output terminals

Answer

Norton current IN is found by short-circuiting the output terminals and calculating the resulting current through that short.

Question 4

In phasor notation, multiplying a phasor by j (the imaginary unit) results in:

Accepted Answer

A 90° phase lead

Answer

Multiplying by j = 1∠90° rotates a phasor counterclockwise by 90°, corresponding to a 90° phase advance (lead).

Question 5

The impedance of a series circuit with R = 3 Ω, XL = 6 Ω, and XC = 2 Ω is:

Accepted Answer

5 Ω at 53.13°

Answer

Z = R + j(XL - XC) = 3 + j4, so |Z| = √(9+16) = 5 Ω and θ = arctan(4/3) ≈ 53.13°.

BEE - Bachelor of Electrical Engineering Practice Test