What is the primary function of an encoder in digital electronics?

The correct answer is C: Convert active input lines into coded output. Encoder produces binary-coded output corresponding to only one active input line among many inputs

The snubber capacitor in a power converter acts to:

The correct answer is B: Limit voltage rise rate (dv/dt) during device turn-off. Snubber capacitors provide a path for displacement current during switching transitions, clamping the voltage and reducing dv/dt stress on semiconductor devices.

A single-phase full-wave bridge rectifier with a 230V AC input produces an average output voltage of approximately:

The correct answer is C: 207 V. For a full-wave rectifier: Vdc = (2√2/π) × Vrms = 0.9 × Vrms = 0.9 × 230 = 207 V approximately.

Which of the following is a state-space representation advantage over transfer function?

The correct answer is B: Can handle multiple inputs and outputs (MIMO systems). State-space representation naturally handles MIMO systems, non-linear systems, and time-varying systems better than transfer functions.

For a Type 2 system with step input, the steady-state error is:

The correct answer is A: Zero. Type 2 systems have zero steady-state error for step input (constant reference), as they have at least 2 poles at origin.

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Electrical Engg (EEE)

Electrical machines, power systems, circuits

321 Q 7 Topics Take Mock Test

Difficulty: All Easy Medium Hard 141–150 of 321

Topics in Electrical Engg (EEE)

All Circuit Analysis 100 Electrical Machines 100 Power Systems 100 Control Systems 100 Power Electronics 100 Electrical Measurements 40 Digital Electronics 100

Q.141 Medium Control Systems

In a compensated system, if phase margin PM = 30° and gain margin GM = 8 dB, this indicates:

A Excellent stability with fast response

B Marginal stability with oscillatory response

C Good stability with acceptable transient response

D Poor stability requiring redesign

Correct Answer: C. Good stability with acceptable transient response

EXPLANATION

PM = 30° is acceptable (typically 30-60°), GM = 8 dB (>6 dB threshold) indicates good gain stability. Both margins suggest satisfactory performance

Test

Q.142 Medium Control Systems

In a unity feedback system, increasing loop gain K generally:

A Increases steady-state error and decreases stability margins

B Decreases steady-state error but may reduce stability margins

C Increases both steady-state error and stability

D Has no effect on steady-state error

Correct Answer: B. Decreases steady-state error but may reduce stability margins

EXPLANATION

Higher K reduces ess proportionally but shifts root locus rightward, potentially crossing into RHP, thus reducing stability margins

Test

Q.143 Medium Control Systems

A system has poles at -2±j3. The natural frequency and damping ratio are approximately:

A ωn = √13, ζ = 0.55

B ωn = √13, ζ = 1.45

C ωn = 5, ζ = 0.4

D ωn = 3, ζ = 0.67

Correct Answer: A. ωn = √13, ζ = 0.55

EXPLANATION

ωn = √(4+9) = √13 ≈ 3.6 rad/s, ζ = 2/√13 ≈ 0.55

Test

Q.144 Medium Control Systems

Which compensator is preferred for improving steady-state error without significantly affecting transient response?

A Lead compensator

B Lag compensator

C PID controller

D Proportional controller

Correct Answer: B. Lag compensator

EXPLANATION

Lag compensator increases DC gain significantly, improving steady-state error, while its phase lag is restricted to lower frequencies, minimizing transient effects

Test

Q.145 Medium Control Systems

For an underdamped second-order system, the relationship between settling time ts and damping ratio ζ is:

A ts ∝ 1/ζ

B ts ∝ ζ

C ts ∝ 1/(ζωn)

D ts ∝ ωn/ζ

Correct Answer: C. ts ∝ 1/(ζωn)

EXPLANATION

Settling time ts ≈ 4/(ζωn) for 2% criterion, thus ts ∝ 1/(ζωn)

Test

Q.146 Medium Control Systems

In state-space representation, if eigenvalues of A matrix are at s = -1, -2, -3, the system is:

A Unstable and uncontrollable

B Stable but may be uncontrollable

C Stable and controllable

D Marginally stable

Correct Answer: B. Stable but may be uncontrollable

EXPLANATION

Stability depends only on eigenvalue locations (all in LHP = stable). Controllability requires rank[B AB A²B] = n, which eigenvalues alone don't determine

Test

Q.147 Medium Control Systems

A lead compensator Gc(s) = K(s+a)/(s+b) where b > a provides maximum phase lead at frequency:

A ωm = √(ab)

B ωm = (a+b)/2

C ωm = a·b

D ωm = b/a

Correct Answer: A. ωm = √(ab)

EXPLANATION

For lead compensator, maximum phase lead occurs at ωm = 1/√(τ₁τ₂) where τ₁ = 1/a and τ₂ = 1/b, giving ωm = √(ab)

Test

Q.148 Medium Control Systems

What is the effect of adding a pole at the origin to a stable open-loop system?

A Increases phase margin, decreases gain margin

B Decreases phase margin, increases gain margin

C Decreases both phase and gain margins

D Increases both margins equally

Correct Answer: C. Decreases both phase and gain margins

EXPLANATION

Adding a pole at origin adds -90° phase shift at all frequencies, decreasing phase margin. It also reduces high-frequency gain, decreasing gain margin

Test

Q.149 Medium Control Systems

For a second-order system with ζ = 0.5 and ωn = 4 rad/s, what is the peak overshoot?

A 16.3%

B 23.5%

C 28.4%

D 35.2%

Correct Answer: A. 16.3%

EXPLANATION

Peak overshoot = exp(-ζπ/√(1-ζ²))·100% = exp(-0.5π/√0.75)·100% ≈ 16.3%

Test

Q.150 Medium Control Systems

In a Bode plot, what is the phase margin when the gain crossover frequency equals the phase crossover frequency?

A 0° always

B 90°

C 180°

D Undefined

Correct Answer: A. 0° always

EXPLANATION

At the gain crossover frequency, magnitude is 0 dB. When this equals phase crossover frequency, the phase is -180°, giving phase margin = -180° - (-180°) = 0°

Test

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