BEE DC and AC Circuit Analysis 2

Question 1

In a series RLC circuit at resonance, what happens to the impedance?

Accepted Answer

Impedance equals resistance R

Answer

At resonance, inductive and capacitive reactances cancel, leaving only the resistance R as the total impedance.

Question 2

A delta-connected load has each branch impedance of 30 Ω. What is the equivalent wye impedance per phase?

Accepted Answer

10 Ω

Answer

For delta-to-wye conversion, Z_Y = Z_Δ / 3, so 30/3 = 10 Ω.

Question 3

What does the time constant τ represent in an RC circuit?

Accepted Answer

Time for voltage to reach 63.2% of its final value

Answer

The time constant τ = RC is the time required for the capacitor voltage to rise to approximately 63.2% (1 - 1/e) of the source voltage.

Question 4

Using mesh analysis, what is the primary variable solved for?

Accepted Answer

Mesh currents

Answer

Mesh analysis assigns a loop current to each independent mesh and solves for those mesh currents using KVL equations.

Question 5

In a purely inductive AC circuit, what is the phase relationship between voltage and current?

Accepted Answer

Voltage leads current by 90°

Answer

In a pure inductor, the induced EMF (voltage) leads the current by 90° due to the inductor's opposition to current change.

BEE - Bachelor of Electrical Engineering Practice Test