BEE DC and AC Circuit Analysis 4

Question 1

A Wheatstone bridge is balanced when which condition is satisfied?

Accepted Answer

R1/R2 = R3/R4

Answer

A Wheatstone bridge is balanced (galvanometer reads zero) when the ratio of resistances in each arm satisfies R1/R2 = R3/R4.

Question 2

What is the significance of the Q-factor (quality factor) in a resonant circuit?

Accepted Answer

It measures the sharpness of resonance and energy storage efficiency

Answer

Q = ω₀L/R (series) represents the ratio of energy stored to energy dissipated per cycle, indicating how sharp the resonance peak is.

Question 3

In a DC transient RL circuit, how many time constants does it take for the current to reach approximately 99.3% of its steady-state value?

Accepted Answer

5τ

Answer

After 5 time constants (5τ = 5L/R), the current reaches 1 - e⁻⁵ ≈ 99.3% of its final value, considered practically at steady state.

Question 4

For maximum power transfer from a source with Thevenin impedance Zth to a load ZL, what condition must hold in AC circuits?

Accepted Answer

ZL = Zth* (complex conjugate)

Answer

Maximum power transfer in AC circuits requires ZL = Zth*, meaning the load impedance equals the complex conjugate of the source impedance.

Question 5

What is the apparent power in an AC circuit with Vrms = 120 V and Irms = 5 A?

Accepted Answer

600 VA

Answer

Apparent power S = Vrms × Irms = 120 × 5 = 600 VA, regardless of the power factor.

BEE - Bachelor of Electrical Engineering Practice Test