50 + Interview Questions in Frequency Response Analysis in Control Systems Page 1 InterviewSolution

1.	The constant M circle for M=1 is the(a) straight line x=-1/2(b) critical point (-1j0)(c) circle with r= 0.33(d) circle with r=0.67I had been asked this question during an interview for a job.Query is from Polar Plots topic in portion Frequency Response Analysis of Control Systems
Answer» RIGHT ANSWER is (a) straight LINE x=-1/2 Explanation: For M =1 the CONSTANT M circle is a straight line at x=-1/2.

Discussion

2.	Assertion (A): All the systems which exhibit overshoot in transient response will also exhibit resonance peak in frequency response.Reason (R): Large resonance peak in frequency response corresponds to a large overshoot in transient response.(a) Both A and R are true and R is the correct explanation of A(b) Both A and R are true and R is not the correct explanation of A(c) A is true but R is false(d) A is false but R is trueI got this question during an internship interview.The origin of the question is Correlation between Time and Frequency Response in portion Frequency Response Analysis of Control Systems
Answer» Correct choice is (a) Both A and R are true and R is the correct explanation of A The explanation: For G<1/√2 frequency parameters ex Mr resonant peak and time response parameters eg. Mp peak overshoot are WELL CORRELATED. For G>1/√2 the resonant peak Mr does not exist and the correlation breaks down. This is not a SERIOUS problem as for this range of G, the step response oscillations are well-damped and Mp is hardly PERCEPTIBLE.

Discussion

3.	Scientist Nyquist have contribution in:(a) Asymptotic plots(b) Polar plots(c) Root locus technique(d) Constant M and n circleI got this question in an interview.I need to ask this question from Frequency Response in section Frequency Response Analysis of Control Systems
Answer» CORRECT answer is (b) POLAR plots The best I can explain: Nyquist PLOT is USED to find the STABILITY of the system by open loop poles and zeroes and the encirclements of the poles and zeroes and satisfying the equation N=P-Z and this is named under the name of scientist Nyquist.

Discussion

4.	OLTF contains one zero in right half of s-plane then(a) Open loop system is unstable(b) Close loop system is unstable(c) Close loop system is unstable for higher gain(d) Close loop system is stableI have been asked this question in an online quiz.My enquiry is from Bode Plots topic in division Frequency Response Analysis of Control Systems
Answer» CORRECT answer is (C) Close LOOP system is unstable for higher gain Explanation: OLTF contains one zero in right half of s-plane then Close loop system is unstable for higher gain.

Discussion

5.	The transfer function of a phase-lead controller is given by(a) (1+aTs)/(1+Ts) , a>1 T>0(b) (1+aTs)/(1+Ts) , a0(c) (1-aTs)/(1+Ts) , a>1 T>0(d) (1±Ts)/(1+Ts) , a0This question was posed to me in unit test.Enquiry is from Experimentation of Transfer Function in division Frequency Response Analysis of Control Systems
Answer» Right choice is (a) (1+aTs)/(1+Ts) , a>1 T>0 The BEST explanation: For the phase LEAD CONTROLLER in which the STABILITY and speed of response is more for the system, the magnitude of the POLE must be greater than the magnitude of the zero.

Discussion

6.	Which one of the following statements is correct for gain margin and phase margin of two closed-loop systems having loop functions G(s) H(s) and exp(-s) G(s) H(s)?(a) Both gain and phase margins of the two systems will be identical(b) Both gain and phase margins of G(s) H(s) will be more(c) Gain margins of the two systems are the same but phase margins of G(s) H(s) will be more(d) Phase margins of the two systems are the same but gain margin of G(s) H(s) will be lessI had been asked this question in examination.This interesting question is from Correlation between Time and Frequency Response in division Frequency Response Analysis of Control Systems
Answer» The correct option is (c) Gain margins of the two systems are the same but phase margins of G(s) H(s) will be more The explanation: The factor exp (-st) is the cause of the term transportation lag (TIME delay). The effect of e^-st term is simply to rotate each point of the G(s) H(s) plot by an angle WT rad in the clockwise direction. So the phase margin of the system reduces as T increases. But SINCE \|e^-s\| =1, therefore the gain margins of both the systems are the same.

Discussion

7.	The unit circle of the Nyquist plot transforms into 0dB line of the amplitude plot of the Bode diagram at(a) 0 frequency(b) Low frequency(c) High frequency(d) Any frequencyThis question was posed to me in an interview.My doubt stems from Polar Plots topic in section Frequency Response Analysis of Control Systems
Answer» Correct CHOICE is (d) Any frequency For explanation I WOULD say: The unit CIRCLE of the Nyquist plot transforms into 0dB line of the amplitude plot of the Bode diagram at any frequency.

Discussion

8.	For all-pass systems:(a) Poles must lie on right of the s-plane(b) Zeroes must lie on the left of s-plane(c) Poles must lie on the left and zeroes on the mirror image of the pole can be on the right(d) None of the mentionedThis question was posed to me during an interview.Enquiry is from All-pass and Minimum-phase Systems in chapter Frequency Response Analysis of Control Systems
Answer» Right choice is (c) Poles must lie on the LEFT and zeroes on the mirror image of the POLE can be on the right The best explanation: For all-pass SYSTEMS poles must lie on the left and zeroes on the mirror image of the pole can be on the right.

Discussion

9.	For a stable closed loop system, the gain at phase crossover frequency should always be:(a) < 20 dB(b) < 6 dB(c) > 6 dB(d) > 0 dBThis question was posed to me in unit test.The origin of the question is Frequency Response topic in portion Frequency Response Analysis of Control Systems
Answer» Correct choice is (d) > 0 dB Best explanation: PHASE crossover frequency is the frequency at which the gain of the SYSTEM must be 1 and for a STABLE system the gain is decibels must be 0 db.

Discussion

10.	The gain margin in dBs of a unity feedback control system whose open loop transfer function, G(s) H(s) =1/s(s+1) is(a) 0(b) 1(c) -1(d) ∞I have been asked this question by my school teacher while I was bunking the class.I'd like to ask this question from Correlation between Time and Frequency Response topic in division Frequency Response Analysis of Control Systems
Answer» RIGHT ANSWER is (d) ∞ Explanation: wpc = ∞ Magnitude of the transfer function =0 Gain MARGIN =∞ DB.

Discussion

11.	The constant M-circle represented by the equation x^^2+2.25x+y^^2=-1.25 has the value of M equal to:(a) 1(b) 2(c) 3(d) 4I got this question during an interview for a job.My question is taken from Bode Plots in portion Frequency Response Analysis of Control Systems
Answer» CORRECT choice is (C) 3 Easy explanation: COMPARING with the M CIRCLE equation we have the value of M =3.

Discussion

12.	If the gain of the open-loop system is doubled, the gain margin(a) Is not affected(b) Gets doubled(c) Becomes half(d) Becomes one-fourthI had been asked this question during an interview.I'm obligated to ask this question of Polar Plots in portion Frequency Response Analysis of Control Systems
Answer» Correct answer is (a) Is not affected Easy explanation: If the GAIN of the open-loop system is DOUBLED, the gain margin gets doubled.

Discussion

13.	A system has poles at 0.01 Hz, 1 Hz and 80Hz, zeroes at 5Hz, 100Hz and 200Hz. The approximate phase of the system response at 20 Hz is :(a) -90°(b) 0°(c) 90°(d) -180°This question was posed to me during an interview for a job.The question is from Bode Plots in portion Frequency Response Analysis of Control Systems
Answer» CORRECT CHOICE is (a) -90° The BEST explanation: Pole at 0.01 Hz gives -180° phase. Zero at 5HZ gives 90° phase THEREFORE at 20Hz -90° phase shift is provided.

Discussion

14.	Assertion (A): Relative stability of the system reduces due to the presence of transportation lag.Reason (R): Transportation lag can be conveniently handled by Bode plot.(a) Both A and R are true but R is correct explanation of A(b) Both A and R are true but R is correct explanation of A(c) A is true but R is false(d) A is false but R is trueThe question was asked in an internship interview.Asked question is from Bode Plots in chapter Frequency Response Analysis of Control Systems
Answer» Right choice is (B) Both A and R are true but R is correct explanation of A Explanation: Transportation lag can be CONVENIENTLY handled on BODE plot as WELL without the need to make any APPROXIMATION.

Discussion

15.	Given a unity feedback control system with G (s) = K/s(s+4), the value of K for which the damping ratio is 0.5.(a) 1(b) 16(c) 64(d) 32The question was posed to me by my school teacher while I was bunking the class.I'm obligated to ask this question of Experimentation of Transfer Function topic in chapter Frequency Response Analysis of Control Systems
Answer» Right ANSWER is (b) 16 The explanation is: The value is FOUND by using the Routh- Hurwitz CRITERIA and equating ONE of the row of the Routh-Hurwitz criteria EQUAL to zero and hence finding the value of K.

Discussion

16.	The equation 2s^4+s^3+3s^2+5s+10=0 has roots in the left half of s–plane:(a) One(b) Two(c) Three(d) FourI got this question in final exam.Question is taken from Experimentation of Transfer Function topic in portion Frequency Response Analysis of Control Systems
Answer» CORRECT choice is (b) Two Explanation: The ROOTS of the EQUATION can be calculated USING Routh-Hurwitz criterion and hence there are 2 sign changes in the first column of the row and therefore the two roots lie on the RIGHT half of s-plane.

Discussion

17.	In a bode magnitude plot, which one of the following slopes would be exhibited at high frequencies by a 4th order all-pole system?(a) -80dB/decade(b) -40 dB/decade(c) 40 dB/decade(d) 80 dB/decadeThis question was addressed to me during a job interview.I'm obligated to ask this question of Bode Plots topic in chapter Frequency Response Analysis of Control Systems
Answer» Correct choice is (a) -80dB/DECADE The explanation: A 4TH ORDER all pole system means that the system must be having no zero or s-term in numerator and s^4 TERMS in denominator. One pole EXHIBITS -20dB/decade slope, so 4 pole exhibits a slope of -80 dB /decade.

Discussion

18.	All pass system and minimum phase system constitute_________________(a) Pole must lie on left plane(b) Minimum phase system(c) Non-minimum phase system(d) Both must lie on right planeI have been asked this question in an interview.My question is based upon All-pass and Minimum-phase Systems in portion Frequency Response Analysis of Control Systems
Answer» Correct OPTION is (c) Non-minimum PHASE system The best explanation: All PASS system and minimum phase system constitute non-minimum phase system.

Discussion

19.	Frequency range of bode magnitude and phases are decided by :(a) The lowest and higher important frequencies of dominant factors of the OLTF(b) The lowest and highest important frequencies of all the factors of the open loop transfer function(c) Resonant frequencies of the second factors(d) None of the aboveThis question was addressed to me in unit test.I want to ask this question from Bode Plots topic in division Frequency Response Analysis of Control Systems
Answer» Correct CHOICE is (d) None of the above The best I can EXPLAIN: T. F. = KP (1+Tds) There is only one ZERO which will give slope of +20dB/decade.

Discussion

20.	Which one of the following statements is correct? Nichol’s chart is useful for the detailed study analysis of:(a) Closed loop frequency response(b) Open loop frequency response(c) Close loop and open loop frequency responses(d) None of the aboveI got this question in semester exam.My question comes from Bode Plots in chapter Frequency Response Analysis of Control Systems
Answer» RIGHT OPTION is (a) Closed loop frequency response For EXPLANATION I would SAY: Nichol’s chart is useful for the detailed study ANALYSIS of closed loop frequency response.

Discussion

21.	Scientist Bode have contribution in :(a) Asymptotic plots(b) Polar plots(c) Root locus technique(d) Constant M and n circleI got this question during an internship interview.The question is from Frequency Response in chapter Frequency Response Analysis of Control Systems
Answer» Right CHOICE is (a) Asymptotic plots To explain: Asymptotic plots are the bode plots that are DRAWN to find the relative STABILITY of the SYSTEM by finding the phase and gain margin and this was invented by Scientist Bode.

Discussion

22.	The impulse response of a LTI system is a unit step function, then the corresponding transfer function is(a) 1/s(b) 1/s^2(c) 1(d) sI have been asked this question in class test.I'm obligated to ask this question of Experimentation of Transfer Function topic in portion Frequency Response Analysis of Control Systems
Answer» Correct choice is (a) 1/s The best EXPLANATION: The impulse response of a LTI SYSTEM is the transfer function itself and hence for the unit step function . As INPUT then the transfer function will be 1/s.

Discussion

23.	The frequency at which the Nyquist diagram cuts the unit circle is known as:(a) Gain crossover frequency(b) Phase crossover frequency(c) Damping frequency(d) Corner frequencyThis question was addressed to me in semester exam.Origin of the question is All-pass and Minimum-phase Systems in chapter Frequency Response Analysis of Control Systems
Answer» Right ANSWER is (a) Gain CROSSOVER frequency Best EXPLANATION: The frequency at which the NYQUIST diagram cuts the unit circle is known as gain cross over frequency.

Discussion

24.	Assertion (A): The phase angle plot in Bode diagram is not affected by the variation in the gain of the system.Reason (R): The variation in the gain of the system has no effect on the phase margin of the system.(a) Both A and R are true but R is correct explanation of A(b) Both A and R are true but R is correct explanation of A(c) A is true but R is false(d) A is false but R is trueThe question was asked in examination.Enquiry is from Bode Plots topic in section Frequency Response Analysis of Control Systems
Answer» Right choice is (c) A is TRUE but R is false The explanation is: The variation in the GAIN of the system has EFFECT on the phase MARGIN but phase plot is not affected.

Discussion

25.	The polar plot of a transfer function passes through the critical point (-1,0). Gain margin is(a) Zero(b) -1dB(c) 1dB(d) InfinityI had been asked this question by my school teacher while I was bunking the class.My question comes from Polar Plots in portion Frequency Response Analysis of Control Systems
Answer» CORRECT choice is (a) Zero Best explanation: Gain margin of a POLAR PLOT passing through the critical POINT is zero.

Discussion

26.	Which one of the following methods can determine the closed loop system resonance frequency operation?(a) Root locus method(b) Nyquist method(c) Bode plot(d) M and N circleThis question was addressed to me in a job interview.Question is taken from Frequency Response in chapter Frequency Response Analysis of Control Systems
Answer» Right choice is (d) M and N circle For EXPLANATION I would SAY: CLOSED loop system resonance FREQUENCY is the frequency at which maximum peak occurs and this frequency of operation can best be determined with the help of M and N circle.

Discussion

27.	If the Nyquist plot of the loop transfer function G (s)H (s) of a closed-loop system encloses the (1, j0) point in the G (s)H (s) plane, the gain margin of the system is(a) Zero(b) Greater than zero(c) Less than zero(d) InfinityThis question was addressed to me during an internship interview.My doubt is from Experimentation of Transfer Function topic in section Frequency Response Analysis of Control Systems
Answer» CORRECT OPTION is (c) Less than zero The BEST I can explain: Nyquist PLOT deals with the OPEN loop poles and zero and equals the encirclements to the open loop poles of the system.

Discussion

28.	Consider the function F (s) =5/s (s^2+s+2), where F (s) is the Laplace transform f (t). Then the final value theorem is equal to(a) 5(b) 5/2(c) Zero(d) InfinityI got this question by my college professor while I was bunking the class.My enquiry is from Experimentation of Transfer Function in chapter Frequency Response Analysis of Control Systems
Answer» Right answer is (b) 5/2 Easiest explanation: Final value theorem is given for the STABLE system only and this is a type 1 system and for step INPUT the final value can be CALCULATED as 5/2.

Discussion

29.	The critical value of gain for a system is 40 and gain margin is 6dB. The system is operating at a gain of:(a) 20(b) 40(c) 80(d) 120The question was asked in exam.Query is from Bode Plots topic in chapter Frequency Response Analysis of Control Systems
Answer» The correct CHOICE is (a) 20 The explanation: GM (dB) = 20log⁡GM GM =2 As we know, GM =K (marginal)/K (desired) K desired =40/2 =20.

Discussion

30.	The phase angle of the system G(s) =s+5/s^2+4s+9;varies between(a) 0° and 90°(b) 0° and -90°(c) 0° and -180°(d) -90° and -180°The question was asked in unit test.My question is based upon Correlation between Time and Frequency Response in chapter Frequency Response Analysis of Control Systems
Answer» CORRECT OPTION is (b) 0° and -90° For EXPLANATION I would say: PHASE = tan^−1−11w−w^3/45−^2.

Discussion

31.	Consider the following statements: The gain margin and phase margin of an unstable system may respectively be 1. Positive, positive 2. Positive, negative 3. Negative, positive 4. Negative, negative Of these statements(a) 1 and 4 are correct(b) 1 and 2 are correct(c) 1, 2 and 3 are correct(d) 2,3 and 4 are correctI had been asked this question during an interview.The above asked question is from Polar Plots in portion Frequency Response Analysis of Control Systems
Answer» CORRECT CHOICE is (d) 2,3 and 4 are correct For explanation: For unstable system the signs of GAIN margin and phase margin are always DIFFERENT or they can both be negative.

Discussion

32.	The LVDT is used in the measurement of:(a) Displacement(b) Acceleration(c) Velocity(d) HumidityThis question was addressed to me in an interview.This key question is from Experimentation of Transfer Function topic in portion Frequency Response Analysis of Control Systems
Answer» Right ANSWER is (a) DISPLACEMENT To ELABORATE: The LVDT is the LINEAR variable differential transformer and it is used to calculate the displacement with the inductor process.

Discussion

33.	For minimum phase systems:(a) Pole must lie on left plane(b) Zeroes must lie on left plane(c) Poles and zeroes must lie on left plane(d) Both must lie on right planeI have been asked this question in semester exam.This question is from All-pass and Minimum-phase Systems in section Frequency Response Analysis of Control Systems
Answer» The correct answer is (C) POLES and zeroes must LIE on LEFT plane The best I can explain: For minimum phase systems poles and zeroes must lie on the RIGHT s-plane.

Discussion

34.	The polar plot of the open loop transfer function of a feedback control system intersects the real axis at -2. The gain margin of the system is(a) -5dB(b) 0dB(c) -6dB(d) 40dBI had been asked this question during an interview.The above asked question is from Polar Plots in division Frequency Response Analysis of Control Systems
Answer» Correct option is (c) -6dB Explanation: GAIN MARGIN of the system is inverse of the intersect on the REAL AXIS and calculated in decibels. G(s) = 1+s / s(1+0.5s).

Discussion

35.	Scientist Evans have contribution in :(a) Asymptotic plots(b) Polar plots(c) Root locus technique(d) Constant M and n circleThe question was posed to me in homework.My question is taken from Frequency Response topic in division Frequency Response Analysis of Control Systems
Answer» Right answer is (C) Root locus technique For explanation I would say: Root locus technique is used to find the transient and steady state response characteristics by finding the locus of the gain of the SYSTEM and this was MADE SCIENTIST EVANS .

Discussion

36.	The range of K for the stability of system is 0
Answer» The correct choice is (a) 10 Easiest EXPLANATION: GAIN MARGIN of the system is 10.

Discussion

37.	Nichol’s chart is useful for the detailed study and analysis of:(a) Closed loop frequency response(b) Open loop frequency response(c) Close loop and open loop frequency responses(d) open loop and Close loop frequency responsesThe question was posed to me by my school principal while I was bunking the class.This is a very interesting question from Bode Plots in chapter Frequency Response Analysis of Control Systems
Answer» The correct choice is (a) Closed loop frequency response To elaborate: Nichol’s CHART is USEFUL for the detailed study and analysis of closed loop frequency response.

Discussion

38.	The transfer function of a system is given by Y(s)/X(s) = e^−0.1s/1+s. If x(t) is 0.5sint, then the phase angle between the output and the input will be:(a) -39.27°(b) -45°(c) -50.73°(d) -90°The question was posed to me during an interview.The question is from Correlation between Time and Frequency Response in portion Frequency Response Analysis of Control Systems
Answer» Right CHOICE is (C) -50.73° To ELABORATE: PHASE angle = -tan^−1-0.1*180°/π w =1 rad/sec Phase angle =-50.73°.

Discussion

39.	Constant M- loci:(a) Constant gain and constant phase shift loci of the closed-loop system.(b) Plot of loop gain with the variation in frequency(c) Circles of constant gain for the closed loop transfer function(d) Circles of constant phase shift for the closed loop transfer functionThis question was addressed to me in examination.Question is taken from Frequency Response topic in division Frequency Response Analysis of Control Systems
Answer» Right choice is (d) Circles of constant phase SHIFT for the closed loop TRANSFER function Easy explanation: By DEFINITION, Constant M LOCI are Circles of constant phase shift for the closed loop transfer function.

Discussion

40.	Constant N-loci:(a) Constant gain and constant phase shift loci of the closed-loop system.(b) Plot of loop gain with the variation in frequency(c) Circles of constant gain for the closed loop transfer function(d) Circles of constant phase shift for the closed loop transfer functionThe question was posed to me by my college professor while I was bunking the class.Question is from Frequency Response in chapter Frequency Response Analysis of Control Systems
Answer» Correct answer is (C) Circles of constant gain for the closed loop transfer function Explanation: Constant N LOCI are the circles of constant gain for the closed loop transfer function and the INTERSECTION point of the M and N is ALWAYS the point (-1,0).

Discussion

41.	All the constant N-circles in G planes cross the real axis at the fixed points. Which are these points?(a) -1 and origin(b) Origin and +1(c) -0.5 and 0.5(d) -1 and +1The question was posed to me in a job interview.I need to ask this question from Bode Plots topic in division Frequency Response Analysis of Control Systems
Answer» Correct answer is (a) -1 and origin Easy explanation: Centre of N CIRCLE is (-1/2, 1/2N) N =tanα Constant –N circles always PASS through (-1, 0) and (0, 0).

Discussion

42.	The corner frequencies are(a) 0 and 1(b) 0 and 2(c) 0 and 1(d) 1 and 2I have been asked this question in exam.My question is based upon Polar Plots topic in division Frequency Response Analysis of Control Systems
Answer» The correct answer is (d) 1 and 2 To EXPLAIN I WOULD SAY: Corner frequency can be calculated by time constant FORM of the transfer function and here the corner frequencies are 1 and 2.

Discussion

43.	The forward path transfer function of a unity feedback system is given by G(s) = 100/(s^2+10s+100). The frequency response of this system will exhibit the resonance peak at:(a) 10 rad/sec(b) 8.66 rad/sec(c) 7.07 rad/sec(d) 5rad/secI had been asked this question in semester exam.My question is taken from Correlation between Time and Frequency Response topic in division Frequency Response Analysis of Control Systems
Answer» RIGHT OPTION is (c) 7.07 rad/sec For explanation: G(s) = 100/(s^2+10s+100) wn = 10rad/sec G = 10/2wn =0.5 wr = 0.707 rad/s.

Discussion

44.	The critical value of gain for the system is 40. The system is operating at a gain of 20. The gain margin of the system is :(a) 2 dB(b) 3 dB(c) 6 dB(d) 4 dBI have been asked this question in an interview.The above asked question is from Correlation between Time and Frequency Response topic in chapter Frequency Response Analysis of Control Systems
Answer» Correct choice is (c) 6 dB To EXPLAIN I would SAY: G.M. =Kmarginal/Kdesire Kmarginal =40 Kdesire = 20 G.M. =2 G.M. (dB) = 6DB.

Discussion

45.	If the gain of the open loop system is doubled, the gain of the system is :(a) Not affected(b) Doubled(c) Halved(d) One fourth of the original valueThis question was posed to me in an interview.This is a very interesting question from Frequency Response topic in section Frequency Response Analysis of Control Systems
Answer» CORRECT option is (a) Not affected The EXPLANATION: Gain of the OPEN loop system is DOUBLED then the gain of the system is not affected as the gain of the system is not dependent on the overall gain of the system.

Discussion

46.	A minimum phase unity feedback system has a bode plot with a constant slope of -20dB/decade for all frequencies. What is the value of the maximum phase margins of the system?(a) 0°(b) 90°(c) -90°(d) 180°I had been asked this question during a job interview.The above asked question is from All-pass and Minimum-phase Systems topic in portion Frequency Response Analysis of Control Systems
Answer» The CORRECT option is (b) 90° Easiest EXPLANATION: For given Bode PLOT, G(s) H(s) =K/jw As H(s) =1 PM (MAXIMUM) =90°.

Discussion

47.	For non-minimum phase systems:(a) Poles and zeroes must lie on the right s-plane(b) Zeroes must lie on right of s-plane(c) Both lie on left of s-plane(d) Poles must be on the left and zeroes can be on the right s –plane.I have been asked this question in an online interview.I would like to ask this question from All-pass and Minimum-phase Systems topic in chapter Frequency Response Analysis of Control Systems
Answer» RIGHT ANSWER is (d) Poles MUST be on the LEFT and zeroes can be on the right s –plane. Easy EXPLANATION: For non-minimum phase systems poles must be on the left and zeroes can be on the right s –plane.

Discussion

48.	The constant N loci represented by the equation x^^2+x+y^^2=0 is for the value of phase angle equal to:(a) -45°(b) 0°(c) 45°(d) 90°I have been asked this question during an internship interview.This interesting question is from Bode Plots topic in chapter Frequency Response Analysis of Control Systems
Answer» CORRECT choice is (d) 90° Explanation: Centre = (-0.5, 0) Centre of N CIRCLE is (-1/2, 1/2N) N =tanα α =90°.

Discussion

49.	The gain margin for the system with open loop transfer function H(s) = G(s) =2(1+s) / s2 is(a) 8(b) 0(c) 1(d) -8The question was asked during an interview.This key question is from Polar Plots topic in section Frequency Response Analysis of Control Systems
Answer» The correct answer is (B) 0 Easiest explanation: Gain margin of a SYSTEM is calculated at the phase cross over frequency and EXPRESSED in DECIBELS.

Discussion

50.	For a type one system, the steady – state error due to step input is equal to(a) Infinite(b) Zero(c) 0.25(d) 0.5I got this question during an online interview.My query is from Experimentation of Transfer Function in portion Frequency Response Analysis of Control Systems
Answer» The correct option is (b) Zero The best explanation: The STEADY state ERROR is defined as the error between the FINAL value and the desired response and the difference in the value of both will be the steady state error DUE to step input for type one system is zero.

Discussion

Explore topic-wise InterviewSolutions in .

The constant M circle for M=1 is the(a) straight line x=-1/2(b) critical point (-1j0)(c) circle with r= 0.33(d) circle with r=0.67I had been asked this question during an interview for a job.Query is from Polar Plots topic in portion Frequency Response Analysis of Control Systems

Scientist Nyquist have contribution in:(a) Asymptotic plots(b) Polar plots(c) Root locus technique(d) Constant M and n circleI got this question in an interview.I need to ask this question from Frequency Response in section Frequency Response Analysis of Control Systems

For a stable closed loop system, the gain at phase crossover frequency should always be:(a) < 20 dB(b) < 6 dB(c) > 6 dB(d) > 0 dBThis question was posed to me in unit test.The origin of the question is Frequency Response topic in portion Frequency Response Analysis of Control Systems

The constant M-circle represented by the equation x^^2+2.25x+y^^2=-1.25 has the value of M equal to:(a) 1(b) 2(c) 3(d) 4I got this question during an interview for a job.My question is taken from Bode Plots in portion Frequency Response Analysis of Control Systems

If the gain of the open-loop system is doubled, the gain margin(a) Is not affected(b) Gets doubled(c) Becomes half(d) Becomes one-fourthI had been asked this question during an interview.I'm obligated to ask this question of Polar Plots in portion Frequency Response Analysis of Control Systems

The equation 2s^4+s^3+3s^2+5s+10=0 has roots in the left half of s–plane:(a) One(b) Two(c) Three(d) FourI got this question in final exam.Question is taken from Experimentation of Transfer Function topic in portion Frequency Response Analysis of Control Systems

Scientist Bode have contribution in :(a) Asymptotic plots(b) Polar plots(c) Root locus technique(d) Constant M and n circleI got this question during an internship interview.The question is from Frequency Response in chapter Frequency Response Analysis of Control Systems

The critical value of gain for a system is 40 and gain margin is 6dB. The system is operating at a gain of:(a) 20(b) 40(c) 80(d) 120The question was asked in exam.Query is from Bode Plots topic in chapter Frequency Response Analysis of Control Systems

The LVDT is used in the measurement of:(a) Displacement(b) Acceleration(c) Velocity(d) HumidityThis question was addressed to me in an interview.This key question is from Experimentation of Transfer Function topic in portion Frequency Response Analysis of Control Systems

Scientist Evans have contribution in :(a) Asymptotic plots(b) Polar plots(c) Root locus technique(d) Constant M and n circleThe question was posed to me in homework.My question is taken from Frequency Response topic in division Frequency Response Analysis of Control Systems

The range of K for the stability of system is 0

The corner frequencies are(a) 0 and 1(b) 0 and 2(c) 0 and 1(d) 1 and 2I have been asked this question in exam.My question is based upon Polar Plots topic in division Frequency Response Analysis of Control Systems

The gain margin for the system with open loop transfer function H(s) = G(s) =2(1+s) / s2 is(a) 8(b) 0(c) 1(d) -8The question was asked during an interview.This key question is from Polar Plots topic in section Frequency Response Analysis of Control Systems

For a type one system, the steady – state error due to step input is equal to(a) Infinite(b) Zero(c) 0.25(d) 0.5I got this question during an online interview.My query is from Experimentation of Transfer Function in portion Frequency Response Analysis of Control Systems