DC and AC Circuit Analysis Flashcards

A Wheatstone bridge is balanced when which condition is satisfied?

Answer: R1/R2 = R3/R4

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

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

Answer: It measures the sharpness of resonance and energy storage efficiency

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

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?

Answer: 5τ

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

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

Answer: ZL = Zth* (complex conjugate)

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

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

Answer: 600 VA

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

Kirchhoff's Voltage Law (KVL) is based on which fundamental principle?

Answer: Conservation of energy

KVL states that the algebraic sum of all voltages around a closed loop equals zero, which reflects conservation of energy in the circuit.

A sinusoidal voltage is expressed as v(t) = 170 sin(377t + 30°) V. What is its RMS value?

Answer: 120.2 V

For a sinusoidal waveform, Vrms = Vpeak / √2 = 170 / 1.414 ≈ 120.2 V.