Question 1

What type transformer most likely has a 1:1 turns ratio?

Accepted Answer

A) power 
B) impedance matching 
C) center tapped 
D) isolation 
A) power 
B) impedance matching 
C) center tapped 
D) isolation

Question 2

-If 10 W of power are applied to the primary of an ideal transformer with a turns ratio of 1:5, the power delivered to the secondary load is ________.

Accepted Answer

A) 0.5 W 
B) 0 W 
C) 10 W 
D) 50 W 
A) 0.5 W 
B) 0 W 
C) 10 W 
D) 50 W

Question 3

A step-up transformer will increase ________ and decrease ________.

Accepted Answer

A) impedance, current 
B) current, voltage 
C) voltage, impedance 
D) current, impedance 
A) impedance, current 
B) current, voltage 
C) voltage, impedance 
D) current, impedance

Question 4

-What is the primary current in Figure 14-1 if   mA and the turns ratio equals 4:1 ?

Accepted Answer

A) 160 mA 
B) 4 mA 
C) 40 mA 
D) 10 mA 
A) 160 mA 
B) 4 mA 
C) 40 mA 
D) 10 mA

Question 5

The phrase ʺMaximum power is delivered to the load when the load resistance equals the source resistanceʺ is a definition of ________.

Accepted Answer

A) Lenzʹs Law 
B) the maximum power transfer theorem 
C) Kirchhoffʹs Law 
D) Ohmʹs Law 
A) Lenzʹs Law 
B) the maximum power transfer theorem 
C) Kirchhoffʹs Law 
D) Ohmʹs Law

Question 6

What is the problem if a power transformer is delivering a low output voltage even though the primary voltage is correct?

Accepted Answer

A) a partially shorted secondary 
B) a shorted primary 
C) an open primary 
D) an open secondary 
A) a partially shorted secondary 
B) a shorted primary 
C) an open primary 
D) an open secondary

Question 7

If a dc voltage is input to a transformerʹs primary, then an ac voltage is induced in its secondary.

Accepted Answer

A) True 
 B)False

Question 8

An ideal transformer has no power loss.

Accepted Answer

A) True 
 B)False

Question 9

If a 12 V battery is connected across the primary of a transformer with a turns ratio of 1:4, then the secondary voltage is ________.

Accepted Answer

A) 3 V 
B) 0 V 
C) 12 V 
D) 48 V 
A) 3 V 
B) 0 V 
C) 12 V 
D) 48 V

Question 10

-In Figure 14-1, if the primary to secondary turns ratio is 9:1 and a 1   load resistor is placed in the secondary, the reflected resistance seen by the primary equals ________.

Accepted Answer

A)    
B)    
C)    
D)    
A)    
B)    
C)    
D)

Question 11

A transformer can be used as an impedance matching device.

Accepted Answer

A) True 
 B)False

Question 12

A step-up transformer will increase ________ and decrease ________.

Accepted Answer

A) power, current 
B) current, impedance 
C) voltage, impedance 
D) voltage, power 
A) power, current 
B) current, impedance 
C) voltage, impedance 
D) voltage, power

Question 13

The measured voltage on the secondary of a given transformer is 0 V. Which of the following could have caused this?

Accepted Answer

A) open secondary 
B) open primary 
C) shorted load 
D) any of the above 
A) open secondary 
B) open primary 
C) shorted load 
D) any of the above

Question 14

-In Figure 14-1, if the secondary current is 50 mA, the primary current is ________.

Accepted Answer

A) 300 mA 
B) 150 mA 
C) 48.7 mA 
D) 50 mA 
A) 300 mA 
B) 150 mA 
C) 48.7 mA 
D) 50 mA

Question 15

A typical transformer fault would be an open winding.

Accepted Answer

A) True 
 B)False

Question 16

A matching transformerʹs primary needs ________ more turns than its secondary to match a   audio signal distribution line to an   speaker.

Accepted Answer

A) 0.013 
B) 8.66 
C) 75 
D) 0.115 
A) 0.013 
B) 8.66 
C) 75 
D) 0.115

Question 17

-What is the primary current in Figure 14-1 if the turns ratio equals 1:3 and   equals 240 mA?

Accepted Answer

A) 1.2 A 
B) 720 mA 
C) 120 mA 
D) 60 mA 
A) 1.2 A 
B) 720 mA 
C) 120 mA 
D) 60 mA

Question 18

Transformer cores are made from laminated iron to reduce losses.

Accepted Answer

A) True 
 B)False

Question 19

When a   load resistor is connected across the secondary winding of a transformer with a turns ratio of 2:1, the source ʺseesʺ a reflected load of ________.

Accepted Answer

A)    
B)    
C)    
D)    
A)    
B)    
C)    
D)

Question 20

-What is the reflected resistance seen by the primary in Figure 14-1 if the turns ratio is 4:1 and IS is 40 mA?

Accepted Answer

A)    
B)    
C)    
D)    
A)    
B)    
C)    
D)

Exam 14: Transformers

What type transformer most likely has a 1:1 turns ratio?

-If 10 W of power are applied to the primary of an ideal transformer with a turns ratio of 1:5, the power delivered to the secondary load is ________.

A step-up transformer will increase ________ and decrease ________.

-What is the primary current in Figure 14-1 if mA and the turns ratio equals 4:1 ?

The phrase ʺMaximum power is delivered to the load when the load resistance equals the source resistanceʺ is a definition of ________.

What is the problem if a power transformer is delivering a low output voltage even though the primary voltage is correct?

If a dc voltage is input to a transformerʹs primary, then an ac voltage is induced in its secondary.

An ideal transformer has no power loss.

If a 12 V battery is connected across the primary of a transformer with a turns ratio of 1:4, then the secondary voltage is ________.

-In Figure 14-1, if the primary to secondary turns ratio is 9:1 and a 1 load resistor is placed in the secondary, the reflected resistance seen by the primary equals ________.

A transformer can be used as an impedance matching device.

A step-up transformer will increase ________ and decrease ________.

The measured voltage on the secondary of a given transformer is 0 V. Which of the following could have caused this?

-In Figure 14-1, if the secondary current is 50 mA, the primary current is ________.

A typical transformer fault would be an open winding.

A matching transformerʹs primary needs ________ more turns than its secondary to match a audio signal distribution line to an speaker.

-What is the primary current in Figure 14-1 if the turns ratio equals 1:3 and equals 240 mA?

Transformer cores are made from laminated iron to reduce losses.

When a load resistor is connected across the secondary winding of a transformer with a turns ratio of 2:1, the source ʺseesʺ a reflected load of ________.

-What is the reflected resistance seen by the primary in Figure 14-1 if the turns ratio is 4:1 and IS is 40 mA?

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

A step-up transformer will increase and decrease .

A step-up transformer will increase and decrease .