SUBJECTS
|
BROWSE
|
CAREER CENTER
|
POPULAR
|
JOIN
|
LOGIN
Business Skills
|
Soft Skills
|
Basic Literacy
|
Certifications
About
|
Help
|
Privacy
|
Terms
|
Email
Search
Test your basic knowledge |
Transformers
Start Test
Study First
Subject
:
engineering
Instructions:
Answer 50 questions in 15 minutes.
If you are not ready to take this test, you can
study here
.
Match each statement with the correct term.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.
This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.
1. The turns of both windings are cut by the same flux; therefore the induced emf in each turn of both windings is the _____.
Same
flux leakage
change the input voltage
Simple Transformer
2. The loss of power required to reverse the core magnatism each time the current reverses. This loss is caused by friction between the molecules of iron as these particles are aligned first in one direction and the in the opposite direct as current dir
Volt-Amperes (Eh-lh=ExLx)
Exciting
Hysteresis
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
3. Transformers with 4800 volt primaries and 120/240 volt secondaries - either pole or subway type - with two secondary windings terminating at internal links which provide for parallel operation of the secondary windings at 120 volts or series operatio
Class 200 transformers
Eh - lH = Ex - lX
Simple Transformer
Step-up
4. Defined as the ratio of the power output to the power input (in a closed circuit containing resistance)
transformers efficiency law
phase
leakage flux
fuse
5. An instrument used to measure electrical current.
Same
continuous path
ammeter
leg(s)
6. A large amount of power wasted with the open-ended core
Exciting Current
current related to voltage law
die to leakage flux
Measuring
7. With no load on the secondary winding - a small current flows in the primary called _____ _____.
Exciting Current
Measuring
fault
grounded (Earthed)
8. A stationary device for transferring alternating current electrical energy from one circuit to another circuit by electromagnetic means.
closed-ended core (square/doughnut shaped)
Volt-Amperes (Eh-lh=ExLx)
Transformer
rating
9. The energy is always transferred without a change in frequency - but usually with changes in _____ and _____.
fault
Secondary
Voltage - Current
10. The formula for the voltage related to turns ratio
Simple Transformer
polarity
flux
Vs Ns = Vp Np
11. Determines if the transformer is a step up or step down transformer
the number of turns of wire in the primary and secondary coils
directly proportional
Choke coil
central magnetic core
12. Is concentrated in the metal core
saturable reactor
open-ended core
Exciting Current
magnetic field
13. The shape of the core of the transformer ensures a ______________ for the magnetic flux with maximum concentration within the core and minimum leakage of the air
continuous path
highly permeable material - iron or stalloy
transformers efficiency law
Vs Ns = Vp Np
14. The turns ratio between the windings (primary & secondary) of a transformer unless otherwise specified.
a magnetic field that varies quickly in direction and stregnth
ratio of a transformer
low rententivity
central magnetic core
15. The current flowing through the primary winding - in response to the applied primary voltage - sets this up
shell core
a magnetic field that varies quickly in direction and stregnth
Kilovolt -- Amperes (kVA)
hysteresis losses (lagging losses)
16. A magnetic field changing with respect to the conductor will generate a _____ in the conductor.
Voltage
low rententivity
a magnetic field that varies quickly in direction and stregnth
constant current transfomers
17. both coils in this core are heavily insulated
Hysteresis
closed-ended core
Secondary
low rententivity
18. A variable transformer is a continuously adjustable _____ - has the primary winding and secondary winding electrically connected.
an iron core and coil
one coils serves as the primary and secondary windings
Autotransformer
closed-ended core
19. has a laminated iron core (layers of metal plates)
Measuring
Electromagnet
closed-ended core
change the input voltage
20. _____ currents are reduced by laminating the core.
a magnetic field that varies quickly in direction and stregnth
the number of turns of wire in the primary and secondary coils
Eddy
grounded system
21. closed core with a top and bottom. It directs the magnetic field towards the primary and secondary coils and increases the field stregnth
highly permeable material - iron or stalloy
closed-ended core (square/doughnut shaped)
How a transformer works
rated KVA of a transformer
22. The output which can be delivered for the time specified at rated secondary voltage and rated frequency without exceeding the specified temperature limitations.
magnetic flux
rated KVA of a transformer
polarity
by using silicon iron core
23. Function of the dielectric oil
central magnetic core
rating
Insulates - cools transformer by convection - dissipates heat
Current
24. The current related to turns ratio law
Ip Ns = Is Np
Transformer
die to leakage flux
25. The winding to which voltage is supplied is called the _____ winding.
Primary
fault
Step-down
Electromagnetic Induction.
26. The relationship between current and voltage in the coils are inverse
grounded (Earthed)
highly permeable material - iron or stalloy
primary coil
current related to voltage law
27. A part of a circuit made of a low melting point material so that it will melt and break the circuit when a specified current exceeded. Always the weakest point in the circuit.
an iron core and coil
fuse
Step-up
Step-down
28. Current flows through the primary winding in response to primary voltage and sets up a magnetic field that varies in direction and stregnth. under the influence of the changing magnetic field an AC voltage/kv is induced across the secondary coil by e
dielectric oil
Ip Ns = Is Np
electromagnetic mutual induction without loosing too much energy
How a transformer works
29. A transformer primary (H) that has 400 turns is wound to step the voltage down from 240 volts to 120 volts. The number or turns (TX) required in the secondary (X) winding is _____.
Eh/Ex=Th/Tx = (240/120 = 400/Tx) - 240 TX = 48000 - Tx = 48000/240 = 200 turns
continuous path
Transformer
Voltage
30. If the transformer is used as a _____ transformer - the high voltage winding is the primary.
closed-ended core
Measuring Equipment
Step-down
ratio of a transformer
31. Connected to earth or to some conducting body which serves in place of the earth.
grounded (Earthed)
Eddy
Eh - lH = Ex - lX
eddy currents
32. A ___________ transformer is a continuously adjustable Autotransformer.
variable
magnetic flux
Current
current related to voltage law
33. Autotransformers are not safe when they supply a _____ voltage from a high voltage source.
Low
copper losses (I2R); hysteresis losses (lagging losses); and eddy current losses (swirling currents)
H1 - h2...
Autotransformer
34. Divergence of the magnetic field causes this
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
leakage flux
Electromagnet
electromagnetic mutual induction without loosing too much energy
35. Provides the ratio between the applied primary voltage and the induced secondary voltage as result of the turns ratio
saturable reactor
by varying the size of the applied DC
voltage ralated to turns ratio
high frequency transformer
36. Instrument transformers reduce high voltages and currents to safe - usable values for the operation of _____ _____.
Measuring Equipment
Hysteresis
current related to voltage law
step-up (high voltage) transformers - step down transformer - autotransformer
37. The characteristic that requires energy to carry out the constant reorientation of the magnetic dipoles in the hysteresis loss
Exciting
Kilovolt -- Amperes (kVA)
coercivity
Primary
38. A transformer rated at 500KVA and below used for voltage transformation on the distribuition system.
dielectric oil
variable
Distribution transformer
hysteresis losses (lagging losses)
39. Reference to a jumper or conductor - to or from a piece of electrical equipment.
constant current transfomers
primary coil
leg(s)
saturable reactor
40. Modern; extremely efficient-more effective coupling between primary and secondary coils; smaller and lighter
grounded system
H1 - h2...
high frequency transformer
primary coil - secondary coil - central magnetic core
41. This core is more efficient than the air core because the iron core in each coil intensifies the magnetic flux in both primary and secondary coils when they become magnetized as current flows through each set of coils
hysteresis losses (lagging losses)
open-ended core
Choke coil
wigginton
42. For a step up and step down transformer if the turns ratio is constant this is the only way to change the output voltage
rating
Measuring
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
change the input voltage
43. Kind of wire is the secondary coil in a transformer
Eh/Ex=Th/Tx
X1 - X2...
thin copper wire coated with insulated material (shellac or enamel)
Voltage
44. Hysteresis Loss can be reduced by using a core with this feature
magnetic flux
low rententivity
phase
open-ended core
45. The simplest type of transformer core
Measuring Equipment
air core
Eh/Ex=Th/Tx
closed-ended core
46. To minimize ________ in transformer construction - the primary and secondary windings are placed on the same leg(s) of the core.
flux leakage
Autotransformer
Volt-Amperes (Eh-lh=ExLx)
H1 - h2...
47. A transformer loses less than _% in energy
grounded (Earthed)
open-ended core
Volt-Amperes (Eh-lh=ExLx)
5
48. The volt-amperes of the primary of a transformer is equal to the _____ - _____ output of the transformer.
saturable reactor
highly permeable material - iron or stalloy
short circuit
Volt-Amperes (Eh-lh=ExLx)
49. A transformer is a device that has no moving parts and that transfers energy from one circuit to another by _____.
Electromagnetic Induction.
Eh/Ex=Th/Tx
low rententivity
short circuit
50. Transformer losses are classified as _____ and _____.
variable transformers
low rententivity
Copper Losses - Core Losses
Electromagnetic Induction.
Sorry!:) No result found.
Can you answer 50 questions in 15 minutes?
Let me suggest you:
Browse all subjects
Browse all tests
Most popular tests
Major Subjects
Tests & Exams
AP
CLEP
DSST
GRE
SAT
GMAT
Certifications
CISSP go to https://www.isc2.org/
PMP
ITIL
RHCE
MCTS
More...
IT Skills
Android Programming
Data Modeling
Objective C Programming
Basic Python Programming
Adobe Illustrator
More...
Business Skills
Advertising Techniques
Business Accounting Basics
Business Strategy
Human Resource Management
Marketing Basics
More...
Soft Skills
Body Language
People Skills
Public Speaking
Persuasion
Job Hunting And Resumes
More...
Vocabulary
GRE Vocab
SAT Vocab
TOEFL Essential Vocab
Basic English Words For All
Global Words You Should Know
Business English
More...
Languages
AP German Vocab
AP Latin Vocab
SAT Subject Test: French
Italian Survival
Norwegian Survival
More...
Engineering
Audio Engineering
Computer Science Engineering
Aerospace Engineering
Chemical Engineering
Structural Engineering
More...
Health Sciences
Basic Nursing Skills
Health Science Language Fundamentals
Veterinary Technology Medical Language
Cardiology
Clinical Surgery
More...
English
Grammar Fundamentals
Literary And Rhetorical Vocab
Elements Of Style Vocab
Introduction To English Major
Complete Advanced Sentences
Literature
Homonyms
More...
Math
Algebra Formulas
Basic Arithmetic: Measurements
Metric Conversions
Geometric Properties
Important Math Facts
Number Sense Vocab
Business Math
More...
Other Major Subjects
Science
Economics
History
Law
Performing-arts
Cooking
Logic & Reasoning
Trivia
Browse all subjects
Browse all tests
Most popular tests