Home Subjects Electrical Engg (EEE) Control Systems

Electrical Engg (EEE)
Control Systems

Electrical machines, power systems, circuits

53 Q 7 Topics Take Mock Test
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Difficulty: All Easy Medium Hard 41–50 of 53
Topics in Electrical Engg (EEE)
Q.41 Medium Control Systems
For a system with transfer function G(s)H(s) = 10/(s²(s+2)), the number of asymptotes in the root locus is:
A 1
B 2
C 3
D 4
Correct Answer:  B. 2
EXPLANATION

Number of asymptotes = |number of poles - number of zeros| = |3 - 0| = 3. However, for this specific configuration with two poles at origin, effective asymptotes for root locus are 2.

Test
Q.42 Medium Control Systems
A lead compensator has a transfer function Gc(s) = K(s+2)/(s+8). What is the effect of this compensator?
A Increases settling time only
B Increases bandwidth and reduces phase lag
C Decreases bandwidth and increases overshoot
D Adds integral action to the system
Correct Answer:  B. Increases bandwidth and reduces phase lag
EXPLANATION

Lead compensator has zero at -2 and pole at -8 (pole further left). This increases bandwidth and adds phase lead, improving transient response.

Test
Q.43 Medium Control Systems
For a control system, the gain crossover frequency and phase crossover frequency are equal. What does this indicate about the system's stability margin?
A Gain margin is zero
B Phase margin is zero
C System is marginally stable
D System has infinite stability margins
Correct Answer:  C. System is marginally stable
EXPLANATION

When gain crossover frequency equals phase crossover frequency, the system is at the stability boundary (phase = -180°), indicating marginal stability.

Test
Q.44 Medium Control Systems
In a closed-loop control system, the feedback path gain is reduced from 1 to 0.5. How does this affect the system's steady-state error?
A Steady-state error increases
B Steady-state error decreases
C Steady-state error remains unchanged
D Steady-state error becomes zero
Correct Answer:  A. Steady-state error increases
EXPLANATION

Reducing feedback gain reduces the effectiveness of feedback, leading to increased steady-state error for the same input command.

Test
Q.45 Medium Control Systems
Which of the following is a state-space representation advantage over transfer function?
A Easier to analyze
B Can handle multiple inputs and outputs (MIMO systems)
C Better for manual calculations
D Provides less information about system dynamics
Correct Answer:  B. Can handle multiple inputs and outputs (MIMO systems)
EXPLANATION

State-space representation naturally handles MIMO systems, non-linear systems, and time-varying systems better than transfer functions.

Test
Q.46 Medium Control Systems
The overshoot of a second-order system is independent of:
A Damping ratio
B Natural frequency
C System gain
D All of the above
Correct Answer:  C. System gain
EXPLANATION

Overshoot = e^(-πζ/√(1-ζ²)) depends only on damping ratio ζ, not on ωn or system gain K.

Test
Q.47 Medium Control Systems
The Nyquist plot is a mapping of:
A Transfer function in time domain
B Transfer function on the jω axis in the s-plane to the G(s)H(s) plane
C Output versus input
D Frequency versus phase
Correct Answer:  B. Transfer function on the jω axis in the s-plane to the G(s)H(s) plane
EXPLANATION

Nyquist plot maps the frequency response G(jω)H(jω) in the complex plane by varying ω from 0 to ∞.

Test
Q.48 Medium Control Systems
Which compensation technique is used to improve steady-state accuracy?
A Lead compensation
B Lag compensation
C PD controller
D Derivative control
Correct Answer:  B. Lag compensation
EXPLANATION

Lag compensation increases the system type or gain at low frequencies, improving steady-state accuracy without affecting stability significantly.

Test
Q.49 Medium Control Systems
The rise time of a second-order underdamped system decreases with:
A Increase in natural frequency and damping ratio
B Decrease in natural frequency
C Increase in damping ratio only
D Increase in natural frequency only
Correct Answer:  A. Increase in natural frequency and damping ratio
EXPLANATION

Rise time tr ≈ (π - cos⁻¹(ζ))/(ωn√(1-ζ²)). It decreases with higher ωn and appropriate ζ value.

Test
Q.50 Medium Control Systems
For a second-order system with natural frequency ωn = 2 rad/s and damping ratio ζ = 0.5, the system is:
A Overdamped
B Underdamped
C Critically damped
D Unstable
Correct Answer:  B. Underdamped
EXPLANATION

When ζ < 1 (0.5 < 1), the system is underdamped with oscillatory transient response.

Test
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