logo
  • Home
  • Test & Rank
  • About
  • Training
  • Programming
  • CS
  • IT
  • IS
  • ECE
  • EEE
  • EE
  • Civil
  • Mechanical
  • Chemical
  • Metallurgy
  • Instrumentation
  • Aeronautical
  • Aerospace
  • Biotechnology
  • Mining
  • Marine
  • Agriculture
  • MCA
  • BCA
  • Internship
  • Jobs
  • Contact

DC Machines Multiple Choice Questions | MCQs | Quiz

DC Machines Interview Questions and Answers
Practice DC Machines questions and answers for interviews, campus placements, online tests, aptitude tests, quizzes and competitive exams.

Get Started

•   DC Machines Construction
•   DC Machines Applications
•   Commutator Assembly - 1
•   Commutator Assembly - 2
•   PMDC Motors
•   Armature Winding
•   Lap Winding
•   Wave Winding
•   EMF & Torque Production-1
•   EMF & Torque Production-2
•   Electromagnetic Power
•   Armature Reaction - 1
•   Armature Reaction - 2
•   Armature Reaction Effects-1
•   Armature Reaction Effects-2
•   Commutation Process - 1
•   Commutation Process - 2
•   Excitation Methods
•   ↓Generator Characteristics↓
•   No Load Characteristics
•   External & Armature
•   Self Excited Generator
•   Separate Excited Generator
•   Graphical Representation
•   Parallel Operation
•   ↓Operating Characteristics↓
•   DC Shunt Motor - 1
•   DC Shunt Motor - 2
•   DC Series Motor - 1
•   DC Series Motor - 2
•   DC Compound Motor - 1
•   DC Compound Motor - 2
•   DC Motor Basics - 1
•   DC Motor Basics - 2
•   DC Motors Starting - 1
•   DC Motors Starting - 2
•   Shunt Motor Speed Control
•   Series Motor Speed Control
•   DC Motor Speed Control
•   Ward Leonard Method
•   DC Motors Braking - 1
•   DC Motors Braking - 2
•   DC Machine Efficiency - 1
•   DC Machine Efficiency - 2
•   Swinburne's Test
•   Hopkinson's Test
•   BLDC Motors
•   ↓ DC Motor Control ↓
•   Control Through Converters
•   Control Through Choppers

Best Reference Books

DC Machines Books
« Prev Page
Next Page »

DC Machines Questions and Answers – Graphical Representation of External Characteristics

Posted on January 19, 2018 by Manish

This set of DC Machines Multiple Choice Questions & Answers (MCQs) focuses on “Graphical Representation of External Characteristics”.

1. No load point of DC generator is __________
a) Intersection of OCC and Rf line
b) Point on the Y axis at rated field current
c) Point on the X axis at rated terminal voltage
d) Can’t find through graphical interpretation
View Answer

Answer: a
Explanation: Intersection of OCC with field resistance line gives the no-load point. All the value so obtained from x and y axis respectively gives the terminal voltage and field current of a DC generator at no-load.
advertisement

2. Rf line intersects with OCC in ________
a) 1st quadrant
b) 2nd quadrant
c) 3rd quadrant
d) 4th quadrant
View Answer

Answer: a
Explanation: Rf line is a straight line passing through the origin and having constant slope, so rising always in a positive direction. OCC starts from some positive value on Y axis and increases till maximum point, afterwards it starts becoming constant, where generally it intersects with Rf line.

3. How armature resistance effect is shown graphically?
a) By adding IaRa product horizontally with Rf line
b) By subtracting IaRa product vertically with Rf line
c) By adding IaRa product vertically with Rf line
d) By subtracting IaRa product horizontally with Rf line
View Answer

Answer: c
Explanation: For representing the voltage drop in armature resistance, we add product IaRa vertically with Rf line at minimum 2 points and draw line parallel to Rf to get line with V + IaRa = constant.

4. For determining IaRa maximum _____________
a) Distance between Rf line and v+ IaRa line is taken
b) Distance between OCC and v+ IaRa line is taken
c) Maximum Distance between OCC and v+ IaRa line is taken
d) Can’t calculated graphically
View Answer

Answer: c
Explanation: OCC when starts from some residual voltage on y axis, goes on increasing till some maximum value and then starts reducing slightly. The bulk is formed where maximum distance between OCC and v+ IaRa line is taken, to get effective frop in armature.
advertisement

5. How demagnetization effect of armature reaction is shown graphically?
a) By shifting origin towards +ve y axis
b) By shifting origin towards +ve x axis
c) By shifting origin towards -ve y axis
d) By shifting origin towards -ve x axis
View Answer

Answer: d
Explanation: The demagnetization caused by armature reaction can be quantified by equivalent field current Ifd which can be taken as proportional to the armature current Ia. So, by shifting the origin towards -ve x axis by Ifd we can show armature reaction graphically.

6. External characteristics of DC shunt motor lies in ______________
a) 1st quadrant
b) 2nd quadrant
c) 1st and 2nd quadrant
d) 4th quadrant
View Answer

Answer: c
Explanation: When external characteristics are plotted on graphs, and if effect of armature reaction is not considered graph lies in 1st quadrant only. When effect of armature reaction is considered we shift the origin thus, characteristics lies in 2nd quadrant as well.

7. From magnetization characteristic at If = 7.1 A, Ea = 225 V at 1000 rpm. What will be the terminal voltage at speed 950 rpm?
a) 225 V
b) 235 V
c) 214 V
d) 220 V
View Answer

Answer: c
Explanation: Speed is directly proportional to the back emf of a machine. So, Ea = 225 V at 1000 rpm
Ea (950 rpm) = 225 x 950 / 1000, this will give speed of given DC machine at 950 rpm. Upon calculations we get, Ea = 213.7 V= 214 V approx.
advertisement

8. For a given compound DC machine, Net field current obtained from characteristic is equal to 7.5 A, where shunt field current is equal to 5 A, armature current is 505 A, demagnetizing current equal to 0.95 A and shunt field winding of 1000 turns at rated speed of 1000 rpm. What will be the series field turns?
a) 7
b) 8
c) 5
d) 9
View Answer

Answer: a
Explanation: From the excitation balance equation, If + [Nse/Nf] Ia – Ifd =If (net).
5 + 505(Nse /1000) – 0.95 = If (net).
Calculating for Nse by substituting If (net), we get Nse = 6.8 that is 7 turns.

Sanfoundry Global Education & Learning Series – DC Machines.

To practice all areas of DC Machines, here is complete set of 1000+ Multiple Choice Questions and Answers.

« Prev Page - DC Machines Questions and Answers – Characteristics of Separately Excited Generators
» Next Page - DC Machines Questions and Answers – Parallel Operation of DC Generator

« DC Machines Questions and Answers – Characteristics of Separately Excited Generators
DC Machines Questions and Answers – Parallel Operation of DC Generator »
advertisement

Deep Dive @ Sanfoundry:

  1. Electrical Machines Questions and Answers
  2. DC Machines Questions and Answers
  3. DC Machines Questions and Answers – Operating Characteristics of DC Series Motor -1
  4. DC Machines Questions and Answers – Operating Characteristics of DC Compound Motor – 2
  5. Electrical Machines Questions and Answers – Two Reaction Theory of Salient Pole Machines
  6. Electrical Machines Questions and Answers – Operating Characteristics of DC Generators
  7. DC Machines Questions and Answers – Characteristics of Separately Excited Generators
  8. DC Machines Questions and Answers – Operating Characteristics of DC Shunt Motor -1
  9. DC Machines Questions and Answers – Characteristics of Self Excited Generator
  10. DC Machines Questions and Answers – No Load with On Load Characteristics of DC Generator
Manish Bhojasia
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Facebook | Twitter

Best Careers

Developer Tracks
SAN Developer
Linux Kernel Developer
Linux Driver Developer
Linux Network Developer

Live Training Photos
Mentoring
Software Productivity
GDB Assignment
Sanfoundry is No. 1 choice for Deep Hands-ON Trainings in SAN, Linux & C, Kernel Programming. Our Founder has trained employees of almost all Top Companies in India such as VMware, Citrix, Oracle, Motorola, Ericsson, Aricent, HP, Intuit, Microsoft, Cisco, SAP Labs, Siemens, Symantec, Redhat, Chelsio, Cavium, ST-Micro, Samsung, LG-Soft, Wipro, TCS, HCL, IBM, Accenture, HSBC, Mphasis, Tata-Elxsi, Tata VSNL, Mindtree, Cognizant and Startups.

Best Trainings

SAN I - Technology
SAN II - Admin
Linux Fundamentals
Advanced C Training
Linux-C Debugging
System Programming
Network Programming
Linux Threads
Kernel Programming
Kernel Debugging
Linux Device Drivers

Best Reference Books

Computer Science Books
Algorithm & Programming Books
Electronics Engineering Books
Electrical Engineering Books
Chemical Engineering Books
Civil Engineering Books
Mechanical Engineering Books
Industrial Engineering Books
Instrumentation Engg Books
Metallurgical Engineering Books
All Stream Best Books

Questions and Answers

1000 C Questions & Answers
1000 C++ Questions & Answers
1000 C# Questions & Answers
1000 Java Questions & Answers
1000 Linux Questions & Answers
1000 Python Questions
1000 PHP Questions & Answers
1000 Hadoop Questions
Cloud Computing Questions
Computer Science Questions
All Stream Questions & Answers

India Internships

Computer Science Internships
Instrumentation Internships
Electronics Internships
Electrical Internships
Mechanical Internships
Industrial Internships
Systems Internships
Chemical Internships
Civil Internships
IT Internships
All Stream Internships

About Sanfoundry

About Us
Copyright
Terms
Privacy Policy
Jobs
Bangalore Training
Online Training
Developers Track
Mentoring Sessions
Contact Us
Sitemap
© 2011 Sanfoundry. All Rights Reserved.