Electrical Engineering questions for GATE, PSU recruitment and SSC JE draw from network theory, electrical machines, power systems, control systems, measurements and instrumentation, analog and digital electronics, and electromagnetic fields. Numerical answers include the formula used and the unit at each stage, which is where marks are commonly lost even when the approach is correct.
In a Bode plot, the magnitude plot slope in dB/decade for a pole at origin is:
Answer: A
Each pole contributes -20 dB/decade slope. A single pole at origin contributes -20 dB/decade.
Q.22Easy
A second-order system has damping ratio ζ = 0.5. This system is classified as:
Answer: B
For ζ < 1, the system is underdamped with oscillatory response. ζ = 0.5 falls in this category.
Q.23Easy
Which of the following is a characteristic of a lag compensator?
Answer: B
Lag compensator reduces steady-state error by increasing the DC gain without significantly affecting transient response or stability margins.
Q.24Easy
For a Type 2 system with step input, the steady-state error is:
Answer: A
Type 2 systems have zero steady-state error for step input (constant reference), as they have at least 2 poles at origin.
Q.25Easy
The transfer function of a proportional-integral (PI) controller is:
Answer: C
PI controller: Gc(s) = Kp(1 + 1/(Tis)) = Kp + Ki/s, where Ki = Kp/Ti eliminates steady-state error for constant inputs.
Q.26Easy
A negative feedback control system has an open-loop transfer function G(s)H(s) = K/[s(s+2)(s+4)]. What is the type of the system?
Answer: B
The system has one pole at origin (s term in denominator), making it a Type 1 system. Type is determined by the number of poles at origin.
Q.27Easy
In Bode plot analysis, what does the gain margin represent?
Answer: B
Gain margin is the reciprocal of the magnitude at the frequency where phase is -180°. It indicates stability margin in dB.
Q.28Easy
The transfer function of an ideal derivative controller is:
Answer: A
A derivative controller has transfer function Gc(s) = Kd·s, where Kd is the derivative gain. It provides leading phase.
Q.29Easy
For a system G(s) = K(s+2)/[s(s+1)(s+3)], the number of asymptotes in root locus is:
Answer: B
Number of asymptotes = |poles - zeros| = |3 - 1| = 2. Three poles, one zero gives 2 asymptotes.
Q.30Easy
In digital control systems, the sampling theorem requires sampling frequency to be:
Answer: A
Nyquist sampling theorem: fs > 2·fmax to avoid aliasing. The sampling frequency must be at least twice the highest frequency component.
Q.31Easy
A second-order system has natural frequency ωn = 10 rad/s and damping ratio ζ = 0.5. The peak overshoot percentage is approximately:
Answer: A
Using the formula for peak overshoot: Mp = exp(-ζπ/√(1-ζ²)) × 100 = exp(-0.5π/√0.75) × 100 ≈ 16.3%. This is independent of ωn.
Q.32Easy
A PID controller Gc(s) = Kp + Ki/s + Kd·s is applied to a process. Which parameter adjustment would primarily reduce steady-state error without affecting transient response significantly?
Answer: B
The integral term (Ki) directly addresses steady-state error by accumulating past errors. Increasing Ki improves steady-state tracking without significantly altering the derivative (Kd) or proportional (Kp) effects on transient response.
