Inst ToolsInst ToolsInst Tools
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Search
  • Books
  • Software
  • Projects
  • Process
  • Tools
  • Basics
  • Formula
  • Power Plant
  • Root Cause Analysis
  • Electrical Basics
  • Animation
  • Standards
  • 4-20 mA Course
  • Siemens PLC Course
Reading: Polar Plots MCQ
Share
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • Design
  • PLC
  • Interview
  • Control System
Search
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Multiple Choice Questions > Polar Plots MCQ

Polar Plots MCQ

Last updated: November 27, 2021 5:40 pm
Editorial Staff
Multiple Choice Questions
No Comments
Share
6 Min Read
SHARE

Polar Plots MCQ

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=0.67

Answer: a

Explanation: For M =1 the constant M circle is a straight line at x=-1/2.

2. The polar plot of a transfer function passes through the critical point (-1,0). Gain margin is

a) Zero
b) -1dB
c) 1dB
d) Infinity

Answer: a

Explanation: Gain margin of a polar plot passing through the critical point is zero.

3. Consider the following statements:
1. The effect of feedback is to reduce the system error
2. Feedback increases the gain of the system in one frequency range but decreases in another
3. Feedback can cause a system that is originally stable to become unstable
Which of these statements are correct.

a) 1,2 and 3
b) 1 and 2
c) 2 and 3
d) 1 and 3

Answer: c

Explanation: Feedback can cause the increase in gain and also can cause stable system to become unstable.

4. The open loop transfer function of a system is G(s) H(s)= K / (1+s)(1+2s)(1+3s) The phase cross over frequency ωc is

a) V2
b) 1
c) Zero
d) V3

Answer: b

Explanation: Phase crossover frequency is calculated as by calculating the magnitude of the transfer function and equating it to 1 and the frequency calculated at this magnitude is phase cross over frequency.

5. 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-fourth

Answer: a

Explanation: If the gain of the open-loop system is doubled, the gain margin gets doubled.

6. 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 frequency

Answer: d

Explanation: The unit circle of the Nyquist plot transforms into 0dB line of the amplitude plot of the Bode diagram at any frequency.

7. 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 correct

Answer: d

Explanation: For unstable system the signs of gain margin and phase margin are always different or they can both be negative.

8. If a system has an open loop transfer function 1-s / 1+s, then the gain of the system at frequency of 1 rad/s will be

a) 1
b) 1/2
c) Zero
d) -1

Answer: d

Explanation: The system is all pass system and the gain of the system at frequency of 1 rad/sec.

9. 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) 40dB

Answer: c

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).

10. The corner frequencies are

a) 0 and 1
b) 0 and 2
c) 0 and 1
d) 1 and 2

Answer: d

Explanation: Corner frequency can be calculated by time constant form of the transfer function and here the corner frequencies are 1 and 2.

11. For the transfer function G(s) H(s) = 1 / s(s+1) (s+0.5), the phase cross-over frequency is

a) 0.5 rad/sec
b) 0.707 rad/sec
c) 1.732 rad/sec
d) 2 rad/sec

Answer: b

Explanation: Phase cross over frequency is calculated at the point where magnitude of the polar plot is 1.

12. The gain margin (in dB) of a system having the loop transfer function G(s) H(s) = 2 / s(s+1) is

a) 0
b) 3
c) 6
d) 8

Answer: d

Explanation: Gain margin of a system is calculated at the phase cross over frequency and expressed in decibels.

13. The gain margin for the system with open loop transfer function G(s) H(s) = G(s) =2(1+s) / s2 is

a) 8
b) 0
c) 1
d) -8

Answer: b

Explanation: Gain margin of a system is calculated at the phase cross over frequency and expressed in decibels.

14. Statement 1: In constant M circles, as M increases from 1 to 8 radius of circle increases from 0 to 8 and Centre shifts from (-1,0) to (-8,0)
Statement 2: The circle intersects real axis at point (-1/2, 0)

a) Statement 1 is TRUE, 2 is FALSE
b) Statement 1 is FALSE, 2 is TRUE
c) Statement 1 & 2 TRUE
d) Statement 1 & 2 FALSE

Answer: d

Explanation: All the circles pass through the points (0,0) and (-1,0).

Don't Miss Our Updates
Be the first to get exclusive content straight to your email.
We promise not to spam you. You can unsubscribe at any time.
Invalid email address
You've successfully subscribed !

Continue Reading

Feedforward Control Questions and Answers
Experimentation of Transfer Function
Performance Indices
Compensation Techniques : Control Systems
Instrumentation Diagrams Multiple Choice Questions
Cascade Compensation in Time Domain
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
Leave a Comment

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
210kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

Online Analyzers Questions & Answers
Observer Systems
Chromatography Questions & Answers
Feedback Compensation
Stepper Motors Objective Questions & Answers
Basic ESR Spectrometer
Gas Chromatograph- Mass Spectrometer
Sulphur Di-oxide Monitoring Questions & Answers

Keep Learning

pH Analyzers Questions and Answers

Hydrogen and Glass Electrodes Questions & Answers

Nonlinear Control Systems

Stability Analysis by Describing Functions

Chromatography Questions & Answers

High Pressure Liquid Chromatography Questions & Answers

Mathematical Models of Physical Systems

Transfer Functions Objective Questions

Nuclear Power Plant Multiple Choice Questions

Nuclear Power Plant Multiple Choice Questions

Time Response Analysis

Time Response of Second Order Systems – I

Induction Motor Interview Questions Answers

Electrical Measurements and Instrumentation Objective Questions & Answers

Time Response Analysis

State Variable Analysis – Part I

Learn More

Parallel Circuit Parallel Current Calculations

Parallel Circuit Current Calculations

Circular Chart Recorder

How to Read Circular Chart Recorder for Flow Measurement?

Power Electronics Objective Questions

Thyristors Objective Questions and Answers

Turbine Flow Meter Calibration

How to do Turbine Flow Meter Verification?

Difference Between Batch Process and Continuous Process

Difference Between Batch Process and Continuous Process

Steam Turbine Driven Centrifugal Compressors Leak due to Broken Instrument

Discharge Head 3‑monthly leaks of Steam Turbine Driven Centrifugal Compressors

RTD Calibration

RTD Calibration

Differences Between AC and DC Motors

Menu

  • About
  • Privacy Policy
  • Copyright

Quick Links

  • Learn PLC
  • Helping Hand
  • Part Time Job

YouTube Subscribe

Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Welcome Back!

Sign in to your account

Username or Email Address
Password

Lost your password?