Deck 19: Circuit Theorems in Ac Analysis

Question 1

The superposition theorem is useful for the analysis only in ac circuits.

Answer 1

False

Question 2

The Norton's equivalent circuit is characterized by the:

A) equivalent voltage source in parallel with an equivalent impedance
B) equivalent voltage source in series with an equivalent impedance
C) equivalent current source in parallel with an equivalent impedance
D) equivalent current source in series with an equivalent impedance

Answer 2

equivalent current source in parallel with an equivalent impedance

Question 3

The superposition theorem is useful for the analysis of multiple source circuits.

Answer 3

True

Question 4

Why is the superposition theorem useful in the analysis of multiple-source circuits?

A) because all sources are openend
B) because all sources are shorted out
C) the circuit can be analyzed one source at a time
D) because only Ohm's law is required

Question 5

Maximum power transfer occurs when the ac impedances are:

A) smaller
B) equal
C) larger
D) complex conjugates

Question 6

If two equal currents are in opposing directions at any instant in time, in a given branch, what is the net current at that instant?

A) 1 A
B) zero
C) the complex conjugate of the two
D) their sum

Question 7

Norton's theorem provides a method for the reduction of any ac circuit to an equivalent form consisting of an equivalent current source in parallel with an equivalent impedance.

Question 8

Maximum power is transferred to a load when the load impedance is a complex conjugate of the output impedance of the driving circuit.

Question 9

In order to get maximum power transfer from a capacitive source, the load must have an impedance that is the complex conjugate of the source impedance.

Question 10

Thevenin's equivalent circuit is the transformation of Norton's equivalent circuit.

Question 11

find the Thevenin impedance Zth).

A) 74.1 246.9° Ω
B) 54.3 247.2° Ω
C) 60 253.1° Ω
D) 44.7 263.4° Ω

Question 12

Figure 19-2
Given the circuit in Figure 19-2, find the total current in the load RL).

A) 3.39 247° mA on a dc level of 8 mA
B) 4 mA
C) 1.69 247.3° mA
D) 5.69 247° mA

Question 13

Figure 19-1
Given the circuit in Figure 19-1, find the total circuit current.

A) 12 mA
B) 9 mA
C) 18.2 mA
D) 6 mA

Question 14

An equivalent voltage source in series with an equivalent impedance means you should solve the problem using:

A) Thevenin's theorem
B) Norton's theorem
C) the superposition theorem
D) Millman's theorem

Question 15

An equivalent circuit is one that produces the same voltage and current to a given load as the original circuit it replaces.

Question 16

Given Figure 19-3, find the Thevenin voltage Vth) for the circuit external to RL.

A) 15 253.1° V
B) 8.3 263.4° V
C) 11.2 263.4° V
D) 13.2 253.1° V

Question 17

Assume you need to find the total impedance between two specific terminals, looking into the open terminals, with all sources zeroed. Which theorem is suggested by these conditions?

A) Norton's theorem
B) Thevenin's theorem
C) total impedance
D) both A and B

Question 18

What is the complex conjugate of 75 Ω + j45 Ω?

A) 75 Ω - j45 Ω
B) -75 Ω + j45 Ω
C) -75 Ω - j45 Ω
D) 45 Ω - j75 Ω

Question 19

The superposition theorem is useful for the analysis of single source-circuits.

Question 20

Thevenin's theorem provides a method for the reduction of any ac circuit to an equivalent voltage source in parallel with an equivalent impedance.

Question 21

-What is the Norton equivalent impedance Zn external to ZL?

A) 10.0 $\Omega \angle$
0°
B) 5.0 $\Omega \angle$
90°
C) 0.47 $\Omega \angle$
-26.6°
D) 11.2 $\Omega \angle$
26.6°

Question 22

When the load is properly chosen for maximum power transfer, the load will appear .

A) imaginary
B) reactive
C) complex
D) totally resistive

Question 23

Figure 19-5
See Figure 19-5. Using the superposition theorem, what is the portion of the current through the capacitor caused by the 10 V 20° voltage source?

A) 0.822 A 29.5°
B) 0.616 A 2129.5°
C) 0.741 A 255.6°
D) 0.5 A 290°

Question 24

When using the superposition theorem in ac network analysis, which one of the following statements is not true?

A) All impedances are replaced by their complex conjugates.
B) Current sources are replaced by short circuits.
C) Voltage sources are replaced by open circuits.
D) Voltage sources are replaced by short circuits.

Question 25

To find Vth, determine the between the two specified terminals.

A) short circuit current
B) open circuit current
C) open circuit voltage
D) short circuit voltage

Question 26

The Norton equivalent circuit and Thevenin equivalent circuit can be found from each other by using .

A) a source transformation
B) the voltage divider rule
C) Kirchhoff's law
D) Ohm's law

Question 27

See Figure 19-6. What is the Norton equivalent current In external to ZL?

A) 0.89 A 23.4°
B) 0.67 A 226.6°
C) 0.67 A 230°
D) 0 A 20°

Question 28

For the circuit with output impedance of 100 Ω- j20 Ω, how much power is delivered to a matched load if the voltage VS = 25 V rms?

A) 1.56 W
B) 6.25 W
C) 3.12 W
D) 12.5 W

Question 29

If the output impedance of a certain circuit is 100 Ω - j20 Ω, what value of load impedance will result in maximum power transfer to the load?

A) 20 Ω - j100 Ω
B) 100 Ω + j20 Ω
C) 20 Ω+ j100 Ω
D) 100 Ω- j20 Ω

Question 30

Figure 19-5
See Figure 19-5. Using the superposition theorem, what is the portion of the current through the capacitor caused by the 5 V 230° voltage source?

A) 0.822 A 29.5°
B) 0.616 A 2129.5°
C) 0.741 A 255.6°
D) 0.89 A 293.4°

Question 31

The only difference in applying network theorems to ac circuits rather than dc circuits is that we will be working with and instead of just resistors and real numbers.

A) impedances, vectors
B) currents, shorts
C) voltages, loads
D) impedances, phasors

Question 32

Given the circuit in Figure , what load value should be used to replace R2 to obtain the maximum power transfer to the load? Determine the type of load, and express the value in rectangular form.

A) 168 Ω - j76.8 Ω
B) 88.1 Ω - j39.4 Ω
C) 168 Ω + j76.8 Ω
D) 64.1 Ω- j73.6 Ω

Question 33

The Norton current is found by calculating the between the marked terminals.

A) source current
B) open circuit voltage
C) short circuit current
D) load current