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. A transformer loses less than _% in energy
5
Hysteresis
grounded system
Insulates - cools transformer by convection - dissipates heat
2. The relationship between amperage flowing through the coils and the number of turns on individual coils is inverse
current related to turns ratio law
Ip Ns = Is Np
How a transformer works
eddy currents
3. The 3 types of transformer power loss
copper losses (I2R); hysteresis losses (lagging losses); and eddy current losses (swirling currents)
closed-ended core (square/doughnut shaped)
Vs Ns = Vp Np
magnetic field
4. The winding of a transformer to which electrical energy is supplied.
continuous path
primary winding
coercivity
Volt-Amperes (Eh-lh=ExLx)
5. A ___________ transformer is a continuously adjustable Autotransformer.
variable
thin copper wire coated with insulated material (shellac or enamel)
Simple Transformer
5
6. With no load on the secondary winding - a small current flows in the primary called _____ _____.
magnetic field
flux
Kilovolt -- Amperes (kVA)
Exciting Current
7. This type of core is moderately efficient due to closing the core and layering design which reduces power loss from less leakage flux which provides a continuous path for magnetic flux and an increase in field strength
Distribution transformer
Low
coercivity
closed-ended core
8. The magnetic lines of force that flow from the north pole of a magnet and return to the south pole.
thin copper wire coated with insulated material (shellac or enamel)
flux
current related to turns ratio law
central magnetic core
9. both coils in this core are heavily insulated
class 400 transformers
flux leakage
closed-ended core
change the input voltage
10. The total numbre of lines or force issuing from a pole. (north or south)
magnetic flux
Choke coil
Electromagnetic Induction.
air core
11. For a step up and step down transformer if the turns ratio is constant this is the only way to change the output voltage
wigginton
change the input voltage
one coils serves as the primary and secondary windings
Low
12. The terminals of the high voltage winding are marked _____.
Measuring
H1 - h2...
Simple Transformer
wigginton
13. Refers to the transformer's ability to avoid power loss (heat)
rated KVA of a transformer
magnetic field
transformers efficiency
saturable reactor
14. A transformer rated at 500KVA and below used for voltage transformation on the distribuition system.
phase
a magnetic field that varies quickly in direction and stregnth
hysteresis losses (lagging losses)
Distribution transformer
15. To prevent injury to personnel when servicing any equipment connected to a current transformer - the secondary winding must be ____ - _____.
Exciting
short circuit
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
16. The winding to which the load is connected is called the _____ winding.
5
Choke coil
Ip Ns = Is Np
Secondary
17. Defined as the ratio of the power output to the power input (in a closed circuit containing resistance)
primary coil
Step-down
the number of turns of wire in the primary and secondary coils
transformers efficiency law
18. A stationary device for transferring alternating current electrical energy from one circuit to another circuit by electromagnetic means.
magnetic flux
variable transformers
Transformer
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
19. _____ shows that the voltamperes of the primary of a transformer equal the voltamperes of the secondary of a transformer.
Autotransformer
fuse
highly permeable material - iron or stalloy
Eh - lH = Ex - lX
20. _____ currents are reduced by laminating the core.
closed-ended core
Eddy
Primary
21. The energy is always transferred without a change in frequency - but usually with changes in _____ and _____.
Voltage - Current
Exciting Current
primary winding
Class 200 transformers
22. The volt-amperes of the primary of a transformer is equal to the _____ - _____ output of the transformer.
fuse
Volt-Amperes (Eh-lh=ExLx)
Ip Ns = Is Np
Simple Transformer
23. 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
Primary
open-ended core
central magnetic core
grounded system
24. Central magnetic core made of
highly permeable material - iron or stalloy
dielectric oil
leg(s)
grounded (Earthed)
25. ___________ is often used in laminated cores - increases electrical resistance which decreases eddy currents
grounded (Earthed)
central magnetic core
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
silicon steel
26. The output rating of a transformer is based upon the maximum _____ the transformer is capable of carrying without exceeding a certain temperature rise.
Distribution transformer
ratio of a transformer
Current
27. Some losses occur in all transformers. These losses are classified as copper losses and _____ losses.
high frequency transformer
Same
CORE: Core losses are caused by eddy currents set up by the magnetic field.
Hysteresis
28. A partial or total local failure in the insulation or continuity of a conductor.
Eddy
short circuit
fault
Low
29. The 4 types of transformer cores
low rententivity
Exciting
ammeter
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
30. A transformer is a device that has no moving parts and that transfers energy from one circuit to another by _____.
Eh - lH = Ex - lX
H1 - h2...
Electromagnetic Induction.
A small three-phase meter used to determine the direction of phase rotation on circuits or transformer banks.
31. Two coils wound on a closed iron core form a ________.
coercivity
Vs Ip = Vp Is
by varying the size of the applied DC
Simple Transformer
32. The current flowing through the primary winding - in response to the applied primary voltage - sets this up
a magnetic field that varies quickly in direction and stregnth
copper losses (I2R); hysteresis losses (lagging losses); and eddy current losses (swirling currents)
primary coil - secondary coil - central magnetic core
variable
33. The 3 principle components of a transformer
primary coil - secondary coil - central magnetic core
low rententivity
class 400 transformers
How a transformer works
34. When an alternating current is applied to the high-voltage (H) winding of a transformer with no load on the secondary (X) winding - a small current - called the _____ current - flows in the primary.
by using silicon iron core
Autotransformer
air core
Exciting
35. How coercivity is minimized
closed-ended core
by using silicon iron core
Exciting
fuse
36. An instrument used to measure electrical current.
the number of turns in the coil
ammeter
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
Eh - lH = Ex - lX
37. The simplest type of transformer core
The ratio of useful power output to its total power input.
change the input voltage
Secondary
air core
38. A magnetic field changing with respect to the conductor will generate a _____ in the conductor.
Secondary
current related to turns ratio law
Current
Voltage
39. A transformer which when supplied from a constant potential source automatically maintans a constant current in its secondary circuit under varying conditions of load impedance. Used on series street light circuits.
The ratio of useful power output to its total power input.
constant current transfomers
Electromagnet
Choke coil
40. Transformer losses are classified as _____ and _____.
Volt-Amperes (Eh-lh=ExLx)
Copper Losses - Core Losses
Kilovolt -- Amperes (kVA)
one coils serves as the primary and secondary windings
41. Modern; extremely efficient-more effective coupling between primary and secondary coils; smaller and lighter
high frequency transformer
Ip Ns = Is Np
Eddy
silicon steel
42. Kind of wire is the secondary coil in a transformer
thin copper wire coated with insulated material (shellac or enamel)
highly permeable material - iron or stalloy
step-up (high voltage) transformers - step down transformer - autotransformer
43. The characteristic that requires energy to carry out the constant reorientation of the magnetic dipoles in the hysteresis loss
ammeter
Voltage
the number of turns of wire in the primary and secondary coils
coercivity
44. A transformer is a device that either increases or decreases alternating current and voltage using this principle
magnetic field
electromagnetic mutual induction without loosing too much energy
grounded (Earthed)
an iron core and coil
45. How coils serve as the primary and secondary windings for an autotransformer
short circuit
closed-ended core
Vs Ns = Vp Np
one coils serves as the primary and secondary windings
46. Reference to a jumper or conductor - to or from a piece of electrical equipment.
Secondary
transformers efficiency law
Primary
leg(s)
47. Provides the ratio between the applied primary voltage and the induced secondary voltage as result of the turns ratio
Eh/Ex=Th/Tx = (240/120 = 400/Tx) - 240 TX = 48000 - Tx = 48000/240 = 200 turns
high frequency transformer
voltage ralated to turns ratio
flux leakage
48. _____ shows that the voltages across the windings of a transformer are directly proportional to the turns in each winding.
leg(s)
Eh/Ex=Th/Tx
the number of turns in the coil
Measuring
49. Divergence of the magnetic field causes this
Transformer
Primary
phase
leakage flux
50. Both the primary and secondary coils in a transformer are arranged around this
open-ended core
central magnetic core
magnetic flux
Step-down
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