The frequency response of a dynamic element shows a constant magnitude ratio at all frequencies. The element exhibits a negative phase shift at all frequencies. The absolute value of the phase shift increases linearly with frequency. The element has the transfer function ?

Related Mcqs:

1. According to Bode stability criterion, a system is unstable, if the open loop frequency response exhibits an amplitude ratio exceeding unity at frequency for which phase lag is_________________?

   A. 0°
   B. 45°
   C. 90°
   D. 180°

2. A first order system with a time constant of 1 min is subjected to frequency response analysis. At an input frequency of 1 radian/min, the phase shift is______________?

   A. 45°
   B. -90°
   C. -180°
   D. -45°

3. “A control system is unstable, if the open loop frequency response exhibits an amplitude ratio exceeding unity at the crossover frequency.” This is _______________ criterion?

   A. Bode stability
   B. Nyquist
   C. Routh stability
   D. None of these

4. An ideal PID controller has the transfer function [1 + (1/0.55) + 0.25]. The frequency at which the magnitude ratio of the controller is 1, is________________?

   A. 0.5/0.2
   B. 0.2/0.5
   C. 0.2 × 0.5
   D. 1/√(0.2 × 0.5)

5. The frequency response of a first order system, has a phase shift with lower and upper bounds given by________________?

   A. – ∞, π/2
   B. -π/2, π/2
   C. -π/2, 0
   D. 0, π/2

6. The experimental response of the controlled variable y(t) for a step change of magnitude ‘P’ in the manipulated variable x(t) is shown below: The appropriate transfer function of the process is_________________?

   A. (Q/P) e-(Q/R)S/(TdS + 1)
   B. (Q/R) e-TdS/(Q/P) (S + 1)
   C. (Q/P) e-TdS/(Q/R) (S + 1)
   D. (Q/R) e-(P/Q)S/(TdS + 1)

7. Suppose that the gain, time constant and dead time of a process with the following transfer function: Gc(s) = 10 exp( – 0.1s)/(0.5s + 1) are known with a possible error of ± 20% of their values. The largest permissible gain Kc of a proportional controller needs to be calculated below taking the values of process gain, time constant and dead time as________________?

   A. 8, 0.6, 0.08
   B. 12, 0.6, 0.12
   C. 8, 0.6, 0.12
   D. 12, 0.4, 0.08

8. In a closed loop system, the process to be controlled is an integrating process with transfer function 1/2s. The controller proposed to be used in an integral controller with transfer function 1/T1s. When a step change in set point is applied to such a closed loop system, the controlled variable will exhibit__________________?

   A. Overdamped response
   B. Underdamped response
   C. Undamped response
   D. Unstable response

9. The initial value (t = 0) of the unit step response of the transfer function [(s + 1)/(2s + 1)] is__________________?

   A. 0
   B. ½
   C. 1
   D. 2

10. Phase lag of the frequency response of a second order system to a sinusoidal forcing function______________?

    A. Is 30°
    B. Is 90° at the most
    C. Approaches 180° asymptotically
    D. Is 120°