Which Boolean algebra theorem states that A + A·B = A?

The correct answer is A: Absorption theorem. The Absorption theorem simplifies expressions of the form A + A·B to just A, eliminating redundant terms.

Which of the following correctly describes the difference between combinational and sequential logic?

The correct answer is B: Sequential logic depends on past inputs and has memory; combinational output depends only on current inputs. Combinational circuits produce outputs based solely on current inputs. Sequential circuits have memory elements (flip-flops) and outputs depend on input history.

The double-field revolving theory is used to analyze:

The correct answer is C: Single-phase induction motors. The double-field revolving theory represents a single-phase AC winding's pulsating magnetic field as two counter-rotating fields, used to analyze single-phase induction motor behavior.

Which type of power system stability is primarily concerned with the system's ability to maintain synchronism after a small disturbance?

The correct answer is B: Steady-state stability. Steady-state stability examines the system's response to small, gradual disturbances, while transient stability deals with large, sudden disturbances.

The no-load core loss in a transformer is primarily due to:

The correct answer is B: Hysteresis and eddy current losses in core. No-load losses consist of hysteresis loss (due to core magnetization reversal) and eddy current loss (due to induced currents in core material). Copper loss occurs only under load.

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Electrical Engg (EEE)
Control Systems

Electrical machines, power systems, circuits

53 Q 7 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 53

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.11 Medium Control Systems

Which of the following correctly represents the Nyquist stability criterion?

A The Nyquist plot must pass through the point (-1, 0j)

B The number of clockwise encirclements of (-1, 0j) equals the number of unstable poles

C The number of counter-clockwise encirclements of (-1, 0j) must equal Z - P

D The plot must always be in the right half plane

Correct Answer: C. The number of counter-clockwise encirclements of (-1, 0j) must equal Z - P

EXPLANATION

Nyquist criterion: N = Z - P, where N is counter-clockwise encirclements, Z is zeros and P is poles in RHP. For stability, Z = 0.

Test

Q.12 Medium Control Systems

For a closed-loop control system with unity feedback, increasing proportional gain K primarily causes:

A Decrease in settling time and increase in overshoot

B Increase in settling time and decrease in overshoot

C No change in system behavior

D Increase in steady-state error

Correct Answer: A. Decrease in settling time and increase in overshoot

EXPLANATION

Increasing K improves system speed (reduces settling time) but reduces stability margin, increasing overshoot and potentially causing instability.

Test

Q.13 Medium Control Systems

In compensator design, if both transient and steady-state improvements are needed, which approach is preferred?

A Lead compensator only

B Lag compensator only

C Lead-lag compensator

D PID controller without compensation

Correct Answer: C. Lead-lag compensator

EXPLANATION

Lead-lag compensator combines lead (improves transient) and lag (improves steady-state) characteristics for overall system improvement.

Test

Q.14 Medium Control Systems

Peak overshoot of underdamped second-order system depends on:

A Damping ratio only

B Natural frequency only

C Both damping ratio and natural frequency

D Loop gain only

Correct Answer: A. Damping ratio only

EXPLANATION

Peak overshoot Mp = e^(-πζ/√(1-ζ²)). It depends only on damping ratio ζ, not on ωₙ.

Test

Q.15 Medium Control Systems

A system with transfer function H(s) = 100/(s² + 10s + 100) has natural frequency ωₙ and damping ratio ζ respectively as:

A ωₙ = 10 rad/s, ζ = 0.5

B ωₙ = 100 rad/s, ζ = 0.1

C ωₙ = 10 rad/s, ζ = 0.707

D ωₙ = 5 rad/s, ζ = 1

Correct Answer: A. ωₙ = 10 rad/s, ζ = 0.5

EXPLANATION

Standard form: ωₙ² = 100, so ωₙ = 10 rad/s. 2ζωₙ = 10, so ζ = 10/(2×10) = 0.5

Test

Q.16 Medium Control Systems

A lead compensator with transfer function Gc(s) = (1 + aTs)/(1 + Ts) where a > 1 provides:

A Phase lag and reduced bandwidth

B Phase lead and improved transient response

C Reduced steady-state error only

D Increased settling time

Correct Answer: B. Phase lead and improved transient response

EXPLANATION

Lead compensator (a > 1) provides phase lead in mid-frequency range, improving transient response and system speed, hence used for transient improvement.

Test

Q.17 Medium Control Systems

In state-space representation, observability matrix rank should be equal to:

A Number of states

B Number of inputs

C Number of outputs

D Number of poles

Correct Answer: A. Number of states

EXPLANATION

For a system to be completely observable, the observability matrix [C; CA; CA²; ...] must have rank equal to n (number of states).

Test

Q.18 Medium Control Systems

The settling time of a second-order underdamped system is approximately given by:

A ts ≈ 4/(ζωₙ)

B ts ≈ 2/(ζωₙ)

C ts ≈ 1/(ζωₙ)

D ts ≈ π/(ωₙ)

Correct Answer: A. ts ≈ 4/(ζωₙ)

EXPLANATION

For 2% criteria, settling time ts ≈ 4/(ζωₙ). This is the standard formula for second-order systems.

Test

Q.19 Medium Control Systems

A control system with gain margin of 6 dB means:

A Gain can be increased by factor of 2

B Gain can be increased by factor of 4

C Gain can be reduced by factor of 2

D Gain can be reduced by factor of 6

Correct Answer: A. Gain can be increased by factor of 2

EXPLANATION

Gain margin in dB = 20log₁₀(GM). Therefore, 6 = 20log₁₀(GM), GM = 10^(6/20) ≈ 2

Test

Q.20 Medium Control Systems

The Nyquist stability criterion states that for stability, the Nyquist plot should not encircle:

A Origin (0,0)

B Point (-1, 0)

C Point (1, 0)

D Point (0, 1)

Correct Answer: B. Point (-1, 0)

EXPLANATION

The Nyquist criterion checks encirclements of the critical point (-1, 0) in the complex plane. No encirclement indicates stability for minimum phase systems.

Test

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Electrical Engg (EEE) Control Systems

Electrical Engg (EEE)
Control Systems