Question 1

To match a 600 Ω audio load to a 4 Ω speaker system, the primary of the impedance matching transformer must have

Accepted Answer

A) 3.06 
B) 12.2 
C) 150 more turns than the secondary. 
D) The primary should have less turns than the secondary. 
A) 3.06 
B) 12.2 
C) 150 more turns than the secondary. 
D) The primary should have less turns than the secondary.

Question 2

The reflected load in a transformer is defined as the actual load as it appears to the source and results from:

Accepted Answer

A) the turns ratio. 
B) the voltage ratio. 
C) the current ratio. 
D) the power ratio. 
A) the turns ratio. 
B) the voltage ratio. 
C) the current ratio. 
D) the power ratio.

Question 3

A step -up transformer will increase and decrease .

Accepted Answer

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

Question 4

-What is the secondary voltage in Figure 14 -1 if the turns ratio is 9:1?

Accepted Answer

A) 26.6 V 
B) 106 V 
C) 53.2 V 
D) 13.3 V 
A) 26.6 V 
B) 106 V 
C) 53.2 V 
D) 13.3 V

Question 5

Only the number of turns in the primary and secondary of a transformer determines the actual secondary voltage.

Accepted Answer

A) True 
 B)False

Question 6

- if there are five times more turns in the primary than in the secondary, then what is the secondary voltage?

Accepted Answer

A) 600 V 
B) 24 V 
C) 120 V 
D) 12 V 
A) 600 V 
B) 24 V 
C) 120 V 
D) 12 V

Question 7

A core material is not always necessary for proper operation of a transformer.

Accepted Answer

A) True 
 B)False

Question 8

-What is the primary current in Figure 14 -1 if IS = 40 mA and the turns ratio equals 4:1 ?

Accepted Answer

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

Question 9

-What is the secondary current in Figure 14 -1 with a 100 Ω load resistor and 3:1 turns ratio?

Accepted Answer

A) 40 mARMS 
B) 400 mARMS 
C) 33 mARMS 
D) 330 mARMS 
A) 40 mARMS 
B) 400 mARMS 
C) 33 mARMS 
D) 330 mARMS

Question 10

-What is the secondary voltage in Figure 14 -1 if the turns ratio is 1:3?

Accepted Answer

A) 240 VRMS 
B) 80 VRMS 
C) 360 VRMS 
D) 40 VRMS 
A) 240 VRMS 
B) 80 VRMS 
C) 360 VRMS 
D) 40 VRMS

Question 11

-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) 4 kΩ 
B) 8 kΩ 
C) 16 kΩ 
D) 12 kΩ 
A) 4 kΩ 
B) 8 kΩ 
C) 16 kΩ 
D) 12 kΩ

Question 12

-the primary to secondary turns ratio is 1:3 and the secondary current equals 120 mA. What is the primary current?

Accepted Answer

A) 180 mA 
B) 40 mA 
C) 360 mA 
D) cannot compute because the voltage is not given 
A) 180 mA 
B) 40 mA 
C) 360 mA 
D) cannot compute because the voltage is not given

Question 13

- the primary to secondary turns ratio is changed to 2.5:1 and the secondary current equals 100 mA. What is the reflected resistance seen by the primary?

Accepted Answer

A) 5 kΩ 
B) 2.5 kΩ 
C) 1.2 kΩ 
D) 3 kΩ 
A) 5 kΩ 
B) 2.5 kΩ 
C) 1.2 kΩ 
D) 3 kΩ

Question 14

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

Question 15

The impedance matching characteristic for a transformer is needed for a situation where maximum power transfer to the load is desired.

Accepted Answer

A) True 
 B)False

Question 16

The turns ratio of a transformer (n)is defined as:

Accepted Answer

A) the number of turns in the secondary multiplied by the number of turns in the primary. 
B) the number of turns in the secondary divided by the number of turns in the primary. 
C) the number of turns in the primary multiplied by the number of turns in the secondary. 
D) the number of turns in the primary divided by the number of turns in the secondary. 
A) the number of turns in the secondary multiplied by the number of turns in the primary. 
B) the number of turns in the secondary divided by the number of turns in the primary. 
C) the number of turns in the primary multiplied by the number of turns in the secondary. 
D) the number of turns in the primary divided by the number of turns in the secondary.

Question 17

-if the secondary current is 50 mA, the primary current is .

Accepted Answer

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

Question 18

Autotransformers cannot be used for isolation purposes since there is only one winding.

Accepted Answer

A) True 
 B)False

Question 19

How can the windings ratio be safely determined for an unmarked transformer?

Accepted Answer

A) Apply known low voltage ac to the primary and measure the secondary output. The ratio of the voltages is the same as the windings ratio. 
B) Standardized wire color codes indicate windings ratio. 
C) The turns ratio is the same as the ratio of primary resistance to secondary resistance ratio. 
D) either A or C 
A) Apply known low voltage ac to the primary and measure the secondary output. The ratio of the voltages is the same as the windings ratio. 
B) Standardized wire color codes indicate windings ratio. 
C) The turns ratio is the same as the ratio of primary resistance to secondary resistance ratio. 
D) either A or C

Question 20

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

Accepted Answer

A) 2 kΩ 
B) 4 kΩ 
C) 500 Ω 
D) 1 kΩ 
A) 2 kΩ 
B) 4 kΩ 
C) 500 Ω 
D) 1 kΩ

To match a 600 Ω audio load to a 4 Ω speaker system, the primary of the impedance matching transformer must have

The reflected load in a transformer is defined as the actual load as it appears to the source and results from:

A step -up transformer will increase and decrease .

-What is the secondary voltage in Figure 14 -1 if the turns ratio is 9:1?

Only the number of turns in the primary and secondary of a transformer determines the actual secondary voltage.

- if there are five times more turns in the primary than in the secondary, then what is the secondary voltage?

A core material is not always necessary for proper operation of a transformer.

-What is the primary current in Figure 14 -1 if IS = 40 mA and the turns ratio equals 4:1 ?

-What is the secondary current in Figure 14 -1 with a 100 Ω load resistor and 3:1 turns ratio?

-What is the secondary voltage in Figure 14 -1 if the turns ratio is 1:3?

-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?

-the primary to secondary turns ratio is 1:3 and the secondary current equals 120 mA. What is the primary current?

- the primary to secondary turns ratio is changed to 2.5:1 and the secondary current equals 100 mA. What is the reflected resistance seen by the primary?

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 .

The impedance matching characteristic for a transformer is needed for a situation where maximum power transfer to the load is desired.

The turns ratio of a transformer (n)is defined as:

-if the secondary current is 50 mA, the primary current is .

Autotransformers cannot be used for isolation purposes since there is only one winding.

How can the windings ratio be safely determined for an unmarked transformer?

When a 1 kΩ load resistor is connected across the secondary winding of a transformer with a turns ratio of 2:1, the source "sees" a reflected load 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

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Exam 14: Transformers

To match a 600 Ω audio load to a 4 Ω speaker system, the primary of the impedance matching transformer must have

The reflected load in a transformer is defined as the actual load as it appears to the source and results from:

A step -up transformer will increase and decrease .

-What is the secondary voltage in Figure 14 -1 if the turns ratio is 9:1?

Only the number of turns in the primary and secondary of a transformer determines the actual secondary voltage.

- if there are five times more turns in the primary than in the secondary, then what is the secondary voltage?

A core material is not always necessary for proper operation of a transformer.

-What is the primary current in Figure 14 -1 if IS = 40 mA and the turns ratio equals 4:1 ?

-What is the secondary current in Figure 14 -1 with a 100 Ω load resistor and 3:1 turns ratio?

-What is the secondary voltage in Figure 14 -1 if the turns ratio is 1:3?

-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?

-the primary to secondary turns ratio is 1:3 and the secondary current equals 120 mA. What is the primary current?

- the primary to secondary turns ratio is changed to 2.5:1 and the secondary current equals 100 mA. What is the reflected resistance seen by the primary?

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 .

The impedance matching characteristic for a transformer is needed for a situation where maximum power transfer to the load is desired.

The turns ratio of a transformer (n)is defined as:

-if the secondary current is 50 mA, the primary current is .

Autotransformers cannot be used for isolation purposes since there is only one winding.

How can the windings ratio be safely determined for an unmarked transformer?

When a 1 kΩ load resistor is connected across the secondary winding of a transformer with a turns ratio of 2:1, the source "sees" a reflected load 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