Question 1

The ____ transformer changes the high voltage of power company distribution lines to the common 240/120-V used to supply power to most homes and many businesses.

Accepted Answer

A)  distribution 
B)  HIVOLT 
C)  residential 
D)  common 
A)  distribution 
B)  HIVOLT 
C)  residential 
D)  common A

Question 2

Almost all nameplates will list the primary voltage, secondary voltage, and ____.

Accepted Answer

A)  serial number 
B)  impedance 
C)  KVA (kilo-volt-amps) rating 
D)  temperature rise 
A)  serial number 
B)  impedance 
C)  KVA (kilo-volt-amps) rating 
D)  temperature rise C

Question 3

____ are one-winding transformers.

Accepted Answer

A)  Megatransformers 
B)  Isolation transformers 
C)  Distribution transformers 
D)  Autotransformers 
A)  Megatransformers 
B)  Isolation transformers 
C)  Distribution transformers 
D)  Autotransformers D

Question 4

Transformers are among the least efficient machines known.

Accepted Answer

A) True 
 B)False

Question 5

Transformer values of voltage, current, and turns can be computed using formulas.

Accepted Answer

A) True 
 B)False

Question 6

Figure 13-17   Find the values specified in the following questions:
-The turns ratio of the first secondary is 1:____.

Accepted Answer

A)  2.14 
B)  3.55 
C)  4.67 
D)  5.77 
A)  2.14 
B)  3.55 
C)  4.67 
D)  5.77

Question 7

Assume an isolation transformer has a primary voltage of 120 V and a secondary voltage of 500 V. The turns ratio is 1:____.

Accepted Answer

A)  0.231 
B)  1 
C)  2.36 
D)  4.17 
A)  0.231 
B)  1 
C)  2.36 
D)  4.17

Question 8

The isolation transformer ____.

Accepted Answer

A)  cannot have a turns ratio of 1:1 
B)  does not actually electrically isolate the primary and secondary windings 
C)  greatly reduces the voltage spike 
D)  greatly prolongs the voltage spike 
A)  cannot have a turns ratio of 1:1 
B)  does not actually electrically isolate the primary and secondary windings 
C)  greatly reduces the voltage spike 
D)  greatly prolongs the voltage spike

Question 9

The ____ current is the amount of current required to magnetize the core of the transformer.

Accepted Answer

A)  primary 
B)  spike 
C)  core 
D)  excitation 
A)  primary 
B)  spike 
C)  core 
D)  excitation

Question 10

Loads that are intended to operate on 120 V connect from the center tap or ____ to one of the secondary lines.

Accepted Answer

A)  positive 
B)  neutral 
C)  negative 
D)  primary 
A)  positive 
B)  neutral 
C)  negative 
D)  primary

Question 11

The nameplate lists the current rating of the windings.

Accepted Answer

A) True 
 B)False

Question 12

Loads that are intended to operate on 120 V, such as water heaters, electric resistance heating units, and central air conditioners, are connected directly across the lines of the secondary.

Accepted Answer

A) True 
 B)False

Question 13

Figure 13-17   Find the values specified in the following questions:
-The number of turns of wire in the first secondary winding is ____.

Accepted Answer

A)  854 
B)  1005 
C)  1277 
D)  1401 
A)  854 
B)  1005 
C)  1277 
D)  1401

Question 14

The ability of one coil to induce a voltage into another coil is called ____ induction.

Accepted Answer

A)  secondary 
B)  core 
C)  primary 
D)  mutual 
A)  secondary 
B)  core 
C)  primary 
D)  mutual

Question 15

A basic law concerning transformers is that all values of a transformer are proportional to its ____ ratio.

Accepted Answer

A)  turns 
B)  induction 
C)  current 
D)  primary 
A)  turns 
B)  induction 
C)  current 
D)  primary

Question 16

When computing the values of a transformer with multiple secondary windings, treat each secondary as part of the transformer group as a whole.

Accepted Answer

A) True 
 B)False

Question 17

Figure 13-17   Find the values specified in the following questions:
-The current flow in the first secondary is ____ A.

Accepted Answer

A)  0.49 
B)  0.56 
C)  0.63 
D)  0.70 
A)  0.49 
B)  0.56 
C)  0.63 
D)  0.70

Question 18

The ____ winding of a transformer is the power input winding.

Accepted Answer

A)  secondary 
B)  primary 
C)  tertiary 
D)  core 
A)  secondary 
B)  primary 
C)  tertiary 
D)  core

Question 19

A good rule for any type of transformer is that power in ____.

Accepted Answer

A)  is slightly greater than power out 
B)  is exponentially greater than power out 
C)  is less than power out 
D)  must equal power out 
A)  is slightly greater than power out 
B)  is exponentially greater than power out 
C)  is less than power out 
D)  must equal power out

Question 20

Figure 13-17   Find the values specified in the following questions:
-The amount of primary current needed to supply the first secondary winding is ____ A.

Accepted Answer

A)  1.51 
B)  2.11 
C)  2.61 
D)  3.01 
A)  1.51 
B)  2.11 
C)  2.61 
D)  3.01

Exam 13: Transformers

The ____ transformer changes the high voltage of power company distribution lines to the common 240/120-V used to supply power to most homes and many businesses.

Almost all nameplates will list the primary voltage, secondary voltage, and ____.

____ are one-winding transformers.

Transformers are among the least efficient machines known.

Transformer values of voltage, current, and turns can be computed using formulas.

Figure 13-17 Find the values specified in the following questions: -The turns ratio of the first secondary is 1:____.

Assume an isolation transformer has a primary voltage of 120 V and a secondary voltage of 500 V. The turns ratio is 1:____.

The isolation transformer ____.

The ____ current is the amount of current required to magnetize the core of the transformer.

Loads that are intended to operate on 120 V connect from the center tap or ____ to one of the secondary lines.

The nameplate lists the current rating of the windings.

Loads that are intended to operate on 120 V, such as water heaters, electric resistance heating units, and central air conditioners, are connected directly across the lines of the secondary.

Figure 13-17 Find the values specified in the following questions: -The number of turns of wire in the first secondary winding is ____.

The ability of one coil to induce a voltage into another coil is called ____ induction.

A basic law concerning transformers is that all values of a transformer are proportional to its ____ ratio.

When computing the values of a transformer with multiple secondary windings, treat each secondary as part of the transformer group as a whole.

Figure 13-17 Find the values specified in the following questions: -The current flow in the first secondary is ____ A.

The ____ winding of a transformer is the power input winding.

A good rule for any type of transformer is that power in ____.

Figure 13-17 Find the values specified in the following questions: -The amount of primary current needed to supply the first secondary winding is ____ A.

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