Question 1

Transformers .

Accepted Answer

A) match the impedance of a source to the impedance of a load 
B) convert a higher voltage into a lower voltage 
C) convert a lower current into a higher current 
D) all of these 
A) match the impedance of a source to the impedance of a load 
B) convert a higher voltage into a lower voltage 
C) convert a lower current into a higher current 
D) all of these

Question 2

In induction heating, the material is heated due to .

Accepted Answer

A) the fact that the material acts like an open 
B) eddy currents 
C) hysteresis 
D) high load reactance 
A) the fact that the material acts like an open 
B) eddy currents 
C) hysteresis 
D) high load reactance

Question 3

-In Figure 14 -1, if the primary to secondary turns ratio is changed to 4:1 and a 1 kΩ load resistor is in the secondary, the secondary current equals .

Accepted Answer

A) 240 mA 
B) 480 mA 
C) 30 mA 
D) 120 mA 
A) 240 mA 
B) 480 mA 
C) 30 mA 
D) 120 mA

Question 4

A step -down transformer could have a primary -secondary turns ratio of 4:1.

Accepted Answer

A) True 
 B)False

Question 5

An ideal 10:1 transformer with 20 VA of power has less than 2 VA on the output.

Accepted Answer

A) True 
 B)False

Question 6

To couple two circuits together with no change in either voltage or current, use .

Accepted Answer

A) a step -down transformer 
B) an isolation transformer 
C) a step -up transformer 
D) a power transformer 
A) a step -down transformer 
B) an isolation transformer 
C) a step -up transformer 
D) a power transformer

Question 7

-What is the reflected resistance seen by the primary in Figure 14 -1 if the turns ratio is 3:1 and IS is 240 mA?

Accepted Answer

A) 9000 Ω 
B) 167 Ω 
C) 1500 Ω 
D) 500 Ω 
A) 9000 Ω 
B) 167 Ω 
C) 1500 Ω 
D) 500 Ω

Question 8

The small dot placed on schematics of transformers indicates:

Accepted Answer

A) the phase of the voltages. 
B) the polarity of the voltages. 
C) the direction of the winding. 
D) all of these. 
A) the phase of the voltages. 
B) the polarity of the voltages. 
C) the direction of the winding. 
D) all of these.

Question 9

A transformer with a turns ratio of 1:1 is often used to isolate a load from a source.

Accepted Answer

A) True 
 B)False

Question 10

A typical transformer fault would be an open winding.

Accepted Answer

A) True 
 B)False

Question 11

Eddy current loss in a transformer is .

Accepted Answer

A) caused by the resistance of the wire 
B) another name for flux leakage loss 
C) due to current flowing in the core 
D) caused by rapid reversal of the magnetic field 
A) caused by the resistance of the wire 
B) another name for flux leakage loss 
C) due to current flowing in the core 
D) caused by rapid reversal of the magnetic field

Question 12

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

Accepted Answer

A) 162 kΩ 
B) 1 kΩ 
C) 111 Ω 
D) 81 kΩ 
A) 162 kΩ 
B) 1 kΩ 
C) 111 Ω 
D) 81 kΩ

Question 13

- if the secondary current is 50 mA, the reflected resistance seen by the primary equals .

Accepted Answer

A) 7.2 kΩ 
B) 14.4 kΩ 
C) 800 Ω 
D) 2.4 kΩ 
A) 7.2 kΩ 
B) 14.4 kΩ 
C) 800 Ω 
D) 2.4 kΩ

Question 14

An air core transformer would most likely be used for:

Accepted Answer

A) impedance matching 
B) isolation. 
C) audio frequencies 
D) radio frequencies. 
A) impedance matching 
B) isolation. 
C) audio frequencies 
D) radio frequencies.

Question 15

A matching transformer's primary needs audio signal distribution line to an 8 Ω speaker. more turns than its secondary to match a 600 Ω

Accepted Answer

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

Question 16

A transformer with a turns ratio of 1:7 is a step down transformer.

Accepted Answer

A) True 
 B)False

Question 17

36 V of dc is applied to a windings ratio of 1:2. What is the secondary voltage?

Accepted Answer

A) something slightly less than 72 V since transformers do have some loss 
B) 144 V 
C) 72 V 
D) none of the above 
A) something slightly less than 72 V since transformers do have some loss 
B) 144 V 
C) 72 V 
D) none of the above

Question 18

The relationship for the voltage ratio (Vsec/Vpri)in a transformer is:

Accepted Answer

A) less than the turns ratio (Nsec/Npri). 
B) the same as the turns ratio (Nsec/Npri). 
C) opposite to the turns ratio (Nsec/Npri). 
D) more than the turns ratio (Nsec/Npri). 
A) less than the turns ratio (Nsec/Npri). 
B) the same as the turns ratio (Nsec/Npri). 
C) opposite to the turns ratio (Nsec/Npri). 
D) more than the turns ratio (Nsec/Npri).

Question 19

An ideal transformer has no power loss.

Accepted Answer

A) True 
 B)False

Question 20

The phrase "Maximum power is delivered to the load when the load resistance equals the source resistance" is a definition of .

Accepted Answer

A) the maximum power transfer theorem 
B) Lenz's Law 
C) Kirchhoff's Law 
D) Ohm's Law 
A) the maximum power transfer theorem 
B) Lenz's Law 
C) Kirchhoff's Law 
D) Ohm's Law

Transformers .

In induction heating, the material is heated due to .

-In Figure 14 -1, if the primary to secondary turns ratio is changed to 4:1 and a 1 kΩ load resistor is in the secondary, the secondary current equals .

A step -down transformer could have a primary -secondary turns ratio of 4:1.

An ideal 10:1 transformer with 20 VA of power has less than 2 VA on the output.

To couple two circuits together with no change in either voltage or current, use .

-What is the reflected resistance seen by the primary in Figure 14 -1 if the turns ratio is 3:1 and IS is 240 mA?

The small dot placed on schematics of transformers indicates:

A transformer with a turns ratio of 1:1 is often used to isolate a load from a source.

A typical transformer fault would be an open winding.

Eddy current loss in a transformer is .

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

- if the secondary current is 50 mA, the reflected resistance seen by the primary equals .

An air core transformer would most likely be used for:

A matching transformer's primary needs audio signal distribution line to an 8 Ω speaker. more turns than its secondary to match a 600 Ω

A transformer with a turns ratio of 1:7 is a step down transformer.

36 V of dc is applied to a windings ratio of 1:2. What is the secondary voltage?

The relationship for the voltage ratio (Vsec/Vpri)in a transformer is:

An ideal transformer has no power loss.

The phrase "Maximum power is delivered to the load when the load resistance equals the source resistance" is a definition of .

Systems, Quantities, and Units

Voltage, Current, and Resistance

Ohms Law, Energy, and Power

Series Circuits

Parallel Circuits

Series-Parallel Circuits

Magnetism and Electromagnetism

Introduction to Alternating Current and Voltage

Capacitors

Rccircuits

Inductors

Rlcircuits

Rlccircuits and Resonance

Time Response of Reactive Circuits

Filters

Exam 14: Transformers

Transformers .

In induction heating, the material is heated due to .

-In Figure 14 -1, if the primary to secondary turns ratio is changed to 4:1 and a 1 kΩ load resistor is in the secondary, the secondary current equals .

A step -down transformer could have a primary -secondary turns ratio of 4:1.

An ideal 10:1 transformer with 20 VA of power has less than 2 VA on the output.

To couple two circuits together with no change in either voltage or current, use .

-What is the reflected resistance seen by the primary in Figure 14 -1 if the turns ratio is 3:1 and IS is 240 mA?

The small dot placed on schematics of transformers indicates:

A transformer with a turns ratio of 1:1 is often used to isolate a load from a source.

A typical transformer fault would be an open winding.

Eddy current loss in a transformer is .

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

- if the secondary current is 50 mA, the reflected resistance seen by the primary equals .

An air core transformer would most likely be used for:

A matching transformer's primary needs audio signal distribution line to an 8 Ω speaker. more turns than its secondary to match a 600 Ω

A transformer with a turns ratio of 1:7 is a step down transformer.

36 V of dc is applied to a windings ratio of 1:2. What is the secondary voltage?

The relationship for the voltage ratio (Vsec/Vpri)in a transformer is:

An ideal transformer has no power loss.

The phrase "Maximum power is delivered to the load when the load resistance equals the source resistance" is a definition of .

Systems, Quantities, and Units

Voltage, Current, and Resistance

Ohms Law, Energy, and Power

Series Circuits

Parallel Circuits

Series-Parallel Circuits

Magnetism and Electromagnetism

Introduction to Alternating Current and Voltage

Capacitors

Rccircuits

Inductors

Rlcircuits

Rlccircuits and Resonance

Time Response of Reactive Circuits

Filters