Question 1

A transformer with an air core, ferrite core, or powdered iron core is used for:

Accepted Answer

A)  audio frequency applications 
B)  power line frequency applications. 
C)  radio frequency applications 
D)  all of the above. 
A)  audio frequency applications 
B)  power line frequency applications. 
C)  radio frequency applications 
D)  all of the above.

Question 2

In a transformer, how will the primary induced voltage be affected, if the secondary current decreases?

Accepted Answer

A)  It will decrease 
B)  It will increase. 
C)  It will remain the same 
D)  It will be canceled. 
A)  It will decrease 
B)  It will increase. 
C)  It will remain the same 
D)  It will be canceled.

Question 3

A transformer that has only one winding is called an) .

Accepted Answer

A)  tapped transformer 
B)  multiple-winding transformer 
C)  nonideal transformer 
D)  autotransformer 
A)  tapped transformer 
B)  multiple-winding transformer 
C)  nonideal transformer 
D)  autotransformer

Question 4

Secondary current in a transformer depends on secondary voltage and load resistance values.

Accepted Answer

A) True 
 B)False

Question 5

When mutual inductance is present, current changing in one circuit causes an induced voltage in the other circuit.

Accepted Answer

A) True 
 B)False

Question 6

Voltage and current in the primary of a step-down transformer equals the voltage and current in the secondary.

Accepted Answer

A) True 
 B)False

Question 7

-If the primary L1 in Figure  has 40 turns and the secondary L2 has 10 turns, what is the reflected resistance into the primary if the load resistance is 120 Ω?

Accepted Answer

A)  1920 Ω 
B)  480 Ω 
C)  30 Ω 
D)  7.5 Ω 
A)  1920 Ω 
B)  480 Ω 
C)  30 Ω 
D)  7.5 Ω

Question 8

A transformer can be used to step-up increase) Power.

Accepted Answer

A) True 
 B)False

Question 9

A transformer can pass an AC voltage from the primary into the secondary winding.

Accepted Answer

A) True 
 B)False

Question 10

What transformer-turns relationship will be needed to match an output impedance of 5 kΩ to an 8 Ω speaker?

Accepted Answer

A)  5:1 
B)  8:1 
C)  25:1 
D)  625:1 
A)  5:1 
B)  8:1 
C)  25:1 
D)  625:1

Question 11

Figure 14-2
-Eddy currents, magnetic flux leakage, winding resistance and hysteresis in a transformer, all contribute to:

Accepted Answer

A)  mutual inductance 
B)  power loss and heat 
C)  power transfer from primary to secondary 
D)  voltage step-up or step-down 
A)  mutual inductance 
B)  power loss and heat 
C)  power transfer from primary to secondary 
D)  voltage step-up or step-down

Question 12

Increasing the number of turns of wire on the secondary of a transformer will:

Accepted Answer

A)  increase the output voltage 
B)  have no effect on the output voltage. 
C)  increase the primary input voltage 
D)  decrease the output voltage. 
A)  increase the output voltage 
B)  have no effect on the output voltage. 
C)  increase the primary input voltage 
D)  decrease the output voltage.

Question 13

A transformer consists of two or more coils, sharing a common core, or placed close together, and are magnetically coupled.

Accepted Answer

A) True 
 B)False

Question 14

A transformer has 430 turns in the primary and 200 turns in the secondary. What is the P-S turns ratio?

Accepted Answer

A)  2.15:1 
B)  1:2.15 
C)  1:30 
D)  230:1 
A)  2.15:1 
B)  1:2.15 
C)  1:30 
D)  230:1

Question 15

With a primary current of 3 A and a 1:3 turns ratio, the output current will be:

Accepted Answer

A)  3 mA 
B)  3 A 
C)  1 A 
D)  333 A 
A)  3 mA 
B)  3 A 
C)  1 A 
D)  333 A

Question 16

In a transformer, the primary and secondary coils are magnetically linked, but they are:

Accepted Answer

A)  mechanically connected 
B)  current connected 
C)  electrically isolated 
D)  always in phase 
A)  mechanically connected 
B)  current connected 
C)  electrically isolated 
D)  always in phase

Question 17

A transformer can be used to step-down decrease) voltage.

Accepted Answer

A) True 
 B)False

Question 18

-If the input voltage Vin) in Figure 14-1 is 120 V rms and the output voltage Vout) is 24 V rms, what is the turns ratio?

Accepted Answer

A)  1.2:1 
B)  120:1 
C)  5:1 
D)  24:1 
A)  1.2:1 
B)  120:1 
C)  5:1 
D)  24:1

Question 19

A transformer has a 1:6 P-S turns ratio and has a primary current of 12 A. What is the secondary current?

Accepted Answer

A)  2 A 
B)  72 A 
C)  12 A 
D)  6 A 
A)  2 A 
B)  72 A 
C)  12 A 
D)  6 A

Question 20

Mutual inductance is defined as the inductance between two coils that are coupled by a magnetic field.

Accepted Answer

A) True 
 B)False

Exam 14: Transformers

A transformer with an air core, ferrite core, or powdered iron core is used for:

In a transformer, how will the primary induced voltage be affected, if the secondary current decreases?

A transformer that has only one winding is called an) .

Secondary current in a transformer depends on secondary voltage and load resistance values.

When mutual inductance is present, current changing in one circuit causes an induced voltage in the other circuit.

Voltage and current in the primary of a step-down transformer equals the voltage and current in the secondary.

-If the primary L1 in Figure has 40 turns and the secondary L2 has 10 turns, what is the reflected resistance into the primary if the load resistance is 120 Ω?

A transformer can be used to step-up increase) Power.

A transformer can pass an AC voltage from the primary into the secondary winding.

What transformer-turns relationship will be needed to match an output impedance of 5 kΩ to an 8 Ω speaker?

Figure 14-2 -Eddy currents, magnetic flux leakage, winding resistance and hysteresis in a transformer, all contribute to:

Increasing the number of turns of wire on the secondary of a transformer will:

A transformer consists of two or more coils, sharing a common core, or placed close together, and are magnetically coupled.

A transformer has 430 turns in the primary and 200 turns in the secondary. What is the P-S turns ratio?

With a primary current of 3 A and a 1:3 turns ratio, the output current will be:

In a transformer, the primary and secondary coils are magnetically linked, but they are:

A transformer can be used to step-down decrease) voltage.

-If the input voltage Vin) in Figure 14-1 is 120 V rms and the output voltage Vout) is 24 V rms, what is the turns ratio?

A transformer has a 1:6 P-S turns ratio and has a primary current of 12 A. What is the secondary current?

Mutual inductance is defined as the inductance between two coils that are coupled by a magnetic field.

Quantities and Units

Voltage, Current, and Resistance

Ohms Law

Energy and Power

Series Circuits

Parallel Circuits

Series-Parallel Circuits

Circuit Theorems and Conversions

Branch, Loop, and Node Analyses

Magnetism and Electromagnetism

Introduction to Alternating Current and Voltage

Capacitors

Inductors

Rc Circuits

Rl Circuits

Rlc Circuits and Resonance

Passive Filters

Circuit Theorems in Ac Analysis

Time Response of Reactive Circuits

Three-Phase Systems in Power Applications

Filters