Steady-State Sinusoidal Analysis

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Questions

Question 1

A sinusoidal voltage is described by the general equation v(t) = Vm cos(ωt + θ). What does the term Vm represent?

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Question 2

What is the correct way to express a sinusoidal function given as sin(z) in terms of a cosine function for uniform phasor analysis?

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Question 3

Given a sinusoidal voltage v(t) = 100 cos(100πt) V, what is its RMS value and the average power it delivers to a 50 ohm resistance?

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Question 4

What is the phasor representation (V) for a sinusoidal voltage v(t) = Vm cos(ωt + θ)?

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Question 5

What is the complex impedance of a capacitor C at an angular frequency ω?

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Question 6

In a series RLC circuit, how is the equivalent impedance (Zeq) calculated from the individual impedances of the resistor (R), inductor (ZL), and capacitor (ZC)?

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Question 7

In a steady-state AC circuit with sinusoidal sources, what is the correct step-by-step procedure for analysis?

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Question 8

A series RLC circuit has R = 100 ohms, L = 0.3 H, and C = 40 microfarads. A voltage source vs(t) = 100 cos(500t + 30 degrees) is applied. What is the phasor current I?

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Question 9

What is the physical meaning of reactive power (Q) in an AC circuit?

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Question 10

The term cos(θ), where θ is the angle by which the current lags the voltage, is known as what in AC power analysis?

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Question 11

A load is described as having a 'leading' power factor. What does this imply about the load and its reactive power Q?

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Question 12

Complex power (S) is defined as S = P + jQ. How can it be calculated using the voltage phasor V and the current phasor I?

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Question 13

For a two-terminal AC circuit, what condition on the load impedance (Zload) relative to the Thévenin impedance (Zt) will result in maximum average power transfer, assuming the load can be any complex value?

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Question 14

A two-terminal circuit has a Thévenin impedance of Zt = 50 - j50 ohms. What purely resistive load (Rload) will receive the maximum possible power from this circuit?

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Question 15

In a balanced wye-connected (Y-connected) three-phase source, what is the phase relationship between the line-to-line voltage Vab and the line-to-neutral voltage Van?

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Question 16

What is the relationship between the magnitude of the line current (IL) and the phase current (I∆) in a balanced delta-connected load?

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Question 17

What is the primary advantage of using a three-phase power distribution system over three separate single-phase systems for delivering the same total power?

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Question 18

What is a significant characteristic of the total instantaneous power delivered to a balanced three-phase load?

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Question 19

To convert a delta-connected load (Z∆) to an equivalent wye-connected load (ZY), what formula should be used?

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Question 20

A balanced positive-sequence wye-connected source with a line-to-neutral voltage of 1000 V at 60 Hz is connected to a balanced wye-connected load where each phase is a 50 ohm resistor in series with a 0.1 H inductor. What is the magnitude of the line current?

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Question 21

What is the RMS value of a triangular voltage waveform that varies linearly from 0 to 3V in 1 second and back to 0 in the next second, with a period of 2 seconds?

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Question 22

What is the phase relationship between the phasor voltage and phasor current for a pure inductance?

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Question 23

What is the phase relationship between the phasor voltage and phasor current for a pure capacitance?

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Question 24

Two loads are connected in parallel to a source. Load A consumes 5 kW at a power factor of 0.5 leading. Load B consumes 5 kW at a power factor of 0.7 lagging. What is the total real power (P) and total reactive power (Q) delivered by the source?

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Question 25

What is the purpose of power-factor correction in industrial applications?

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Question 26

A 50-kW load operates from a 60-Hz line with a power factor of 60 percent lagging. What is the reactive power of the load?

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Question 27

What is the relationship between the period T and the angular frequency ω for a sinusoidal signal?

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Question 28

For a sinusoidal voltage v(t) = 155.6 cos(377t - 108 degrees) V, what is the frequency in hertz?

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Question 29

What is the equivalent impedance Zeq of a 100 ohm resistor in parallel with a capacitor whose impedance is -j100 ohms?

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Question 30

When using phasors to add sinusoids, what condition must be true for all the sinusoidal terms?

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Question 31

A voltage v1(t) leads another voltage v2(t) by 60 degrees. What does this mean in terms of their peaks on a time plot?

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Question 32

In a node-voltage analysis of a steady-state AC circuit, what do the node equations sum?

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Question 33

What are the standard units for real power (P), reactive power (Q), and apparent power respectively?

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Question 34

The power triangle relates real power P, reactive power Q, and apparent power. For an inductive load, how are these quantities arranged?

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Question 35

How is the Thévenin voltage (Vt) for a steady-state AC circuit determined?

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Question 36

A circuit has a Thévenin impedance Zt = 70.71 ∠-45 degrees ohms. What is the complex load impedance Zload required for maximum power transfer?

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Question 37

A balanced three-phase source has line-to-neutral voltages of 440 V rms. What is the magnitude of the rms line-to-line voltage?

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Question 38

In a balanced wye-wye system, the neutral current is zero. What is the consequence of this for the physical circuit?

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Question 39

For a series RLC circuit, at what frequency is the impedance purely resistive?

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Question 40

What is the result of adding the two sinusoids v1(t) = 20 cos(ωt - 45 degrees) and v2(t) = 10 sin(ωt + 60 degrees)?

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Question 41

In a parallel RLC circuit, what is the relationship between the currents IR (through resistor), IL (through inductor), and IC (through capacitor) and the total current I from the source?

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Question 42

What is the Norton equivalent current (In) for a two-terminal AC network?

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Question 43

A balanced three-phase source is said to have a 'positive phase sequence'. What does this mean?

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Question 44

In a balanced wye-connected system, what is the total average power delivered to the load, in terms of the RMS line-to-neutral voltage (VYrms), RMS line current (ILrms), and power factor angle (θ)?

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Question 45

An AC voltage source V = 707.1 ∠40 degrees delivers 5 kW to a load with a power factor of 20 percent lagging. What is the approximate reactive power Q delivered?

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Question 46

What happens to the impedance of an ideal inductor and an ideal capacitor as the frequency approaches zero (DC)?

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Question 47

What happens to the impedance of an ideal inductor and an ideal capacitor as the frequency approaches infinity?

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Question 48

A sinusoidal voltage v(t) has an RMS value of 10 V, a period of 100 ms, and reaches a positive peak at t = 20 ms. Which expression correctly represents v(t)?

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Question 49

For a series resonant circuit with L = 20 mH, R = 28.28 ohms, and C = 1000 pF, what is the approximate resonant frequency?

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Question 50

A load has an impedance of Z = 100 - j50 ohms. The current flowing through it is I = 15*sqrt(2) ∠30 degrees A. What is the power factor of the load?

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