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# MCQ in AC Circuits Part 4 | REE Board Exam

This is the Multiple Choice Questions Part 4 of the Series in AC Circuits as one of the Electrical Engineering topic. In Preparation for the REE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Exam Questions in Electrical Engineering field, Electrical Engineering Books, Journals and other Electrical Engineering References.

#### Continue Practice Exam Test Questions Part 4 of the Series

SINUSOIDAL VOLTAGE AND CURRENT

Choose the letter of the best answer in each questions.

151.ย  The maximum value of a sine wave AC voltage which will produce heat in a resistor at the same average rate as 115 V of direct current is ____.

A.ย  81.3 V

B.ย  115 V

C.ย  162.6 V

D.ย  230 V

Solution:

152.ย  A sinusoidal voltage source has a peak value of 150 volts. What equivalent DCย  voltageย  sourceย  wouldย  produceย  theย  sameย  heatingย  effectย  inย  aย  1-ohm resistor?

A.ย  15 V

B.ย  212 V

C.ย  95 V

D.ย  106 V

Solution:

153.ย  Theย  effectiveย  valueย  ofย  v(t)ย  =ย  100ย  +ย  Aย  sinย  ฯtย  isย  knownย  toย  beย  103.1.ย  The amplitude A of the sine term is ____.

A.ย  25

B.ย  4.85

C.ย  35.48

D.ย  100

Solution:

154.ย  Anย  alternating current and a direct current flow simultaneously in the same conductor. If the effective of the AC is 8 A and DC is 12 A, what will an AC ammeter read when connected in the circuit?

A.ย  14.42 A

B.ย  12 A

C.ย  11.66 A

D.ย  16.49 A

Solution:

155.ย  Find the reading of an AC voltmeter connected across the series source of 100 sin (ฯt โ ฯ/2) and 100 sin ฯt.

A.ย  100

B.ย  130.65

C.ย  170.71

D.ย  184.78

Solution:

156.ย  A voltage is given be v = 100 sin 314t. How long does it take this wave to complete one fourth of a cycle?

A.ย  20 ms

B.ย  10 ms

C.ย  5 ms

D.ย  1 ms

Solution:

157.ย  When a 15 V square wave is connected across a 50 volt AC voltmeter, it will read _____.

A.ย  21.21 V

B.ย  10.61 V

C.ย  15 V

D.ย  9.55 V

Solution:

158.ย  Calculateย  theย  effectiveย  value ofย  v(t) =ย  100ย  sinย  400tย  + 50 sinย  800tย  +ย  10ย  cos 1200t V.

A.ย  79.5 V

B.ย  57.9 V

C.ย  112.25 V

D.ย  121. 52 V

Solution:

159.ย  Theย  magneticย  fieldย  energyย  of anย  inductorย  changesย  fromย  maximumย  valueย  to minimum value in 5 ms when connected to an ac source. The frequency of the source is

A.ย  20 Hz

B.ย  50 Hz

C.ย  200 Hz

D.ย  500 Hz

Solution:

160.ย  Non-sinusoidal waveforms are made up of

A.ย  different sinusoidal waveforms

B.ย  fundamental and even harmonics

C.ย  fundamental and odd harmonics

D.ย  even and odd harmonics only

Solution:

161.ย  The positive and negative halves of a complex wave are symmetrical when

A.ย  it contains even harmonics

B.ย  phase difference between even harmonics and fundamental is 0 or ฯ

C.ย  it contains odd harmonics

D.ย  phase difference between even harmonies and fundamental is either ฯ/2 or 3ฯ/2

Solution:

162.ย  Theย  r.m.s.ย  valueย  ofย  theย  complexย  voltageย  givenย  by v = 16โ2 sin ฯt + 12โ2 sin 3ฯt is

A.ย  20โ2

B.ย  20

C.ย ย  28 โ2

D.ย  192

Solution:

163.ย  Inย  aย  3-phaseย  system,ย  ____thย  harmonicย  hasย  negativeย  phaseย  sequenceย  of RBY.

A.ย  9

B.ย  13

C.ย  5

D.ย  15

Solution:

164.ย  Aย  complexย  currentย  waveย  isย  givenย  byย  theย  equation i = 14 sin ฯt + 2 sin 5ฯt . The r.m.s. value of the current is ____ ampere.

A.ย  16

B.ย  12

C.ย  10

D.ย  8

Solution:

165.ย  When pure inductive coil is fed by a complex voltage wave, its current wave

A.ย  has larger harmonic content

B.ย  is more distorted

C.ย  is identical with voltage wave

D.ย  shows less distortion

Solution:

166.ย  A complex voltage wave is applied across a pure capacitor. As compared to the fundamental voltage, the reactance offered by the capacitor to the third harmonic voltage would be

A.ย  nine times

B.ย  three times

C.ย  one-third

D.ย  one-ninth

Solution:

167.ย  Whichย  ofย  theย  followingย  harmonicย  voltageย  componentsย  inย  aย  3-phaseย  system would be in phase with each other?

A.ย  3rd, 9th, 15th etc.

B.ย  7th, 13th, 19th etc.

C.ย  5th, 11th, 17th etc.

D.ย  2nd, 4th, 6th etc.

Solution:

168.ย  An alternating voltage is one that

A.ย  varies continuously in magnitude

B.ย  reverses periodically in polarity

C.ย  never varies in magnitude

D.ย  both A and B

Solution:

169.ย  Oneย  completeย  revolutionย  ofย  aย  conductorย  loopย  throughย  aย  magneticย  fieldย  is called a(n)

A.ย  octave

C.ย  cycle

D.ย  alternation

Solution:

170.ย  For a sine wave, one half cycle is often called a(n)

A.ย  alternation

B.ย  harmonic

C.ย  octave

D.ย  period

Solution:

171.ย  For a sine wave, the number of complete cycles per second is called the

A.ย  period

B.ย  wavelength

C.ย  frequency

D.ย  phase angle

Solution:

172.ย  To compare the phase angle between two waveforms, both must have

A.ย  the same amplitude

B.ย  the same frequency

C.ย  different frequency

D.ย  both A and B

Solution:

173.ย  The value of alternating current or voltage that has the same heating effect as a corresponding dc value is known as the

A.ย  peak value

B.ย  average value

C.ย  rms value

D.ย  peak-to-peak value

Solution:

174.ย  For an ac waveform, the period refers to

A.ย  the number of complete cycles per second

B.ย  the length of time required to complete one cycle

C.ย  the time it takes for the waveform to reach its peak value

D.ย  none of these

Solution:

175.ย  The wavelength of a radio wave is

A.ย  inversely proportional to its frequency

B.ย  directly proportional to its frequency

C.ย  inversely proportional to its amplitude

D.ย  unrelated to its frequency

Solution:

176.ย  Unless indicated otherwise, all sine wave ac measurements are in

A.ย  peak-to-peak values

B.ย  peak values

C.ย  rms values

D.ย  average values

Solution:

177.ย  Aย  unitย  stepย  voltageย  isย  appliedย  acrossย  anย  inductor.ย  Theย  currentย  throughย  the inductor will be

A.ย  zero for all time

B.ย  a step function

C.ย  a ramp function

D.ย  a delta (impulse) function

Solution:

178.ย  Aย  rampย  currentย  flowingย  throughย  anย  initiallyย  relaxedย  capacitorย  will resultย  in a voltage across it that

A.ย  varies inversely with time

B.ย  remains constant

C.ย  varies directly with time

D.ย  varies as the square of time

Solution:

179.ย  The voltage v(t) = t u(t) volts is connected across a 1 H inductor having an initial current of -1 A. The net current will be zero at time t equal to

A.ย  0

B.ย ย  1โ2ย  seconds

C.ย  โ2ย  seconds

D.ย  1 second

Solution:

180.ย  A voltage waveform v (t) = 12t2 is applied across 1H inductor for t โฅ 0, with initial current through itย  being zero. The current through the inductor for tย  โฅย  0 is given by

A.ย  12t

B.ย  24t

C.ย  12t3

D.ย  4 t3

Solution:

181.ย  It is desired to have a constant direct current i(t) through the ideal inductor L. The nature of the voltage source v(t) must

A.ย  constant voltage

B.ย  linearly increasing voltage

C.ย  an ideal impulse

D.ย  exponentially increasing voltage

Solution:

182.ย  For the current and voltage waveforms, identify the element & its value.

A.ย  L, 25 H

B.ย  C, 25 F

C.ย  L, 2ย  H

D.ย  C, 2 F

Solution:

183.ย  The voltage and current waveforms for an element are shown inย  theย  figure. Find the circuit element and its value.

A.ย  L and 25 H

B.ย  C and 25 F

C.ย  L and 1 H

D.ย  C and 1 F

Solution:

184.ย  Whatย  isย  theย  rmsย  valueย  ofย  aย  squareย  waveย  withย  anย  amplitudeย  ofย  10ย  Aย  and frequency of 1 Hz?

A.ย  0 A

B.ย  10 A

C.ย  5 A

D.ย  7.07 A

Solution:

185.ย  What is the frequency in kHz of a radio signal whose wavelength is 15 m?

A.ย  10,000

B.ย  20,000

C.ย  15,000

D.ย  20,500

Solution:

SERIES CIRCUITS

186.ย  REE Board Exam September 2003

The following are in series R = 1,000 ฮฉ, L = .100 ฮผH and C = 20,000 pF. The voltageย  acrossย  theย  circuitย  isย  100ย  V,ย  60ย  kHz.ย  Whatย  isย  theย  totalย  impedance expressed in ohms?

A.ย  1882 ohms

B.ย  1000 ohms

C.ย  2132 ohms

D.ย  1885 ohms

Solution:

187.ย  REE Board Exam October 2000

A series circuit has an applied voltage of v = 220 sin (ฯt + 30ยฐ) and draws a current of i = 10 sin (ฯt – 30ยฐ). What is the average power and power factor of the circuit?

A.ย  1,905 W, 86.6% lagging

B.ย  1,905 W, 86.6% lagging

C.ย  2,200 W, 100%

D.ย  1,100 W, 50% lagging

Solution:

188.ย  REE Board Exam September 2001

A coil has an impedance of 75.4 ฮฉ when connected a across a source of 60 Hz. The same coil yields an impedance of 54.8 ฮฉ when connected across a source having a different frequency of 30 Hz. What is the coilโs inductance?

A.ย  245.7 mH

B.ย  512.8 mH

C.ย  158.6 mH

D.ย  341.7 mH

Solution:

189.ย  REE Board Exam April 1996

A circuit consists of a 4 ohms resistor and a 300 ฮผF capacitor in series. It is connected across a 60 Hz voltage source with a 500 V peak voltage. What is the phasor form of the current?

A.ย  I = 19.57โ 57.5ยฐ A

B.ย  I = 8.84โ 73.2ยฐ A

C.ย  I = 36.5โ 65.7ยฐ A

D.ย  I = 10.5โ 65.7ยฐ A

Solution:

190.ย  REE Board Exam September 2000

Find the power in a circuit if i(t) = 10 sin (ฯtย  –ย  30ยฐ) and v(t) = 220 sin (ฯt +30ยฐ).

A.ย  550 watts

B.ย  2200 watts

C.ย  1900 watts

D.ย  1500 watts

Solution:

191.ย  REE Board Exam April 1997

A current of 2.5 A flows through a series circuit consisting of a 100 ฮฉ resistor andย  anย  unknownย  capacitorย  acrossย  aย  sourceย  ofย  460ย  V,ย  50ย  Hz.ย  Whatย  isย  the value of the capacitive reactance?

A.ย  XC = 91.86 ฮฉ

B.ย  XC = 39.19 ฮฉ

C.ย  XC = 154.45 ฮฉ

D.ย  XC = 184.0 ฮฉ

Solution:

192.ย  REE Board Exam April 1995

In a series RC circuit the voltage across theย  capacitor and the resistor are 60 volts and 80 volts respectively. The total voltage is

A.ย  70

B.ย  100

C.ย  140

D.ย  none of these

Solution:

193.ย  EE Board Exam October 1984

An industrial coil has a resistance of 32 ohms and reactance of 24 ohms and rated 440ย  voltsย  atย  60ย  Hz.ย  Aย  factoryย  will connectย  theย  coil toย  aย  440ย  V,ย  50ย  Hz supply. Solve for the value of a series resistor needed to avoid over-current condition.

A.ย  2.07 ohms

B.ย  2.64 ohms

C.ย  2.44 ohms

D.ย  2.25 ohms

Solution:

194.ย  REE Board Exam October 1998

Twoย  relaysย  eachย  withย  20ย  ohmsย  resistanceย  andย  0.16ย  Hย  inductanceย  are connected in series. What is the equivalent impedance?

A.ย  20 + j102.2 ฮฉ

B.ย  20 + j95.32 ฮฉ

C.ย  40 + j120.63 ฮฉ

D.ย  40 + j25.32 ฮฉ

Solution:

195.ย  EE Board Exam October 1990

Anย  inductiveย  coilย  takesย  aย  currentย  ofย  2ย  Aย  andย  consumesย  160ย  Wย  when connected to a 240 V ac supply. A second coil when connected across the same supply takes 3 A and 500 W. Find the total power when the two coils are connected in series to this supply,

A.ย  144.56 W

B.ย  134.31 W

C.ย  150.22 W

D.ย  128.35 W

Solution:

196.ย  EE Board Exam October 1985

A coil draws 1875 watts when connected to a 150 V dc source. It consumes 30.72 watts when use on a 240 V, 60 Hz ac source. Find the inductance of the coil.

A.ย  0.0255 H

B.ย  0.0341 H

C.ย  0.0153 H

D.ย  0.0240 H

Solution:

197.ย  REE Board Exam October 1994

Aย  currentย  ofย  10ย  Aย  andย  a powerย  factorย  ofย  0.8ย  laggingย  isย  takenย  formย  aย  single phase 250 volt supply. The reactive power of the system is

A.ย  1500 vars

B.ย  2000 vars

C.ย  2500 vars

D.ย  none of these

Solution:

198.ย  REE Board Exam October 1996

The resistor of 6 ฮฉ and unknown impedance coil in series draws 12 A from a 120 V, 60 Hz line. If the real power taken from the line is 1152 watts, what is the coil inductance?

A.ย  15.9 mH

B.ย  10 mH

C.ย  20 mH

D.ย  1.59 mH

Solution:

199.ย  REE Board Exam April 1997

Determine the power factor angle in the series circuit which consists of R = 25 ฮฉ, L = 0.2 H, across a power supply of 200 V, 30 Hz.

A.ย  36.4ยฐ

B.ย  46.4ยฐ

C.ย  52.4ยฐ

D.ย  56.4ยฐ

Solution:

200.ย  EE Board Exam April 1993

The impedance coils absorbs 250 watts whenย  connected across 220 V, 60 Hz mains. It is then connected across 110 V, 25 Hz mains and also absorbs 250 watts. What is the inductance of the coil?

A.ย  0.125 H

B.ย  0.149 H

C.ย  0.154 H

D.ย  0.163 H

Solution:

#### Questions and Answers in AC Circuits

Following is the list of practice exam test questions in this brand new series:

MCQ in AC Circuits
PART 1: MCQ from Number 1 โ 50                  Answer key: included
PART 2: MCQ from Number 51 โ 100              Answer key: included
PART 3: MCQ from Number 101 โ 150            Answer key: included
PART 4: MCQ from Number 151 โ 200            Answer key: included
PART 5: MCQ from Number 201 โ 250             Answer key: included
PART 6: MCQ from Number 251 โ 300             Answer key: included
PART 7: MCQ from Number 301 โ 350             Answer key: included
PART 8: MCQ from Number 351 โ 400             Answer key: included
PART 9: MCQ from Number 401 โ 450             Answer key: included
PART 10: MCQ from Number 451 โ 500           Answer key: included

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