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# MCQ in AC Circuits Part 10 | REE Board Exam

This is the Multiple Choice Questions Part 10 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 10 of the Series

RESONANCE

Choose the letter of the best answer in each questions.

451.ย  EE Board Exam April 1993

Capacitor ofย 30-microfarad capacitanceย isย inย seriesย withย a coil across an 8,000 cycle supply. What inductance is required for resonance?

A.ย  13.34 ฮผH

B.ย  10.45 ฮผH

C.ย  13.19 ฮผH

D.ย ย ย  12.55 ฮผH

452.ย  REE Board Exam October 1998

One leg of a radio tuned circuit has a capacitance of 1 x 10-9 F. It is tuned at 200 kHz. What is the inductance of the other leg in Henry?

A.ย  6.33 x 10-4 H

B.ย  20 x 10-3 H

C.ย  8.25 x 10-5 H

D.ย  120 x 10-3 H

Solution:

453.ย  EE Board Exam April 1988

A loud speaker whose inductance is 1.15 Henry is coupled to a power tube throughย  aย  condenserย  ofย  2ย  ฮผFย  capacity.ย  Toย  whatย  frequencyย  willย  the combination be resonant?

A.ย  110 Hz

B.ย  108 Hz

C.ย  105 Hz

D.ย  100 Hz

Solution:

454.ย  REE Board Exam April 1995

What capacitance must be placed in series with an inductance of 0.05 Henry so that at 100 Hz, the impedance becomes equal to the ohmic resistance?

A.ย  50.7 ฮผF

B.ย  35.5 ฮผF

C.ย  70.7 ฮผF

D.ย  87.0 ฮผF

Solution:

455.ย  EE Board Exam April 1989

A coil has a resistance of 50 ohms and a reactance of 100 ohms,ย  is shunted by a capacitor,ย  which has practically no losses in order that the voltage across the coil be in phase with the total current supplied toย the parallel combination.ย  What is the impedance of the parallel combination under the given condition?

A.ย  250 ohms

B.ย  200 ohms

C.ย  230 ohms

D.ย  220 ohms

Solution:

456.ย  EE Board Exam April 1983

Aย  non-inductive resistorย  Rย  is connected in parallel with an inductive reactance ofย  10 ohms. The combination is then connected in series with a capacitive reactance of 5 ohms. Solve for Rย  at which the power factor of the given circuit would be unity.

A.ย  10 ฮฉ

B.ย  12 ฮฉ

C.ย  13 ฮฉ

D.ย  11 ฮฉ

Solution:

457.ย  EE Board Exam October 1982

Two impedances Z1ย  = 15 + j20 and Z2ย  = 5ย  โย  jXCย  are connected in parallel. Solve for the values of XCย  so that the total current drawn by the combination will be in phase with any supply voltage V.

A.ย  28.54 ฮฉ

B.ย  30.43 ฮฉ

C.ย  33.12 ฮฉ

D.ย  29.55 ฮฉ

Solution:

458.ย  EE Board Exam April 1985

A resistance of 5 ohms is connected in series with a capacitor of 442.1ย  ฮผF. Theย combination is then connectedย  inย  parallel with anย inductanceย ofย 21.22 mH. Solve for the frequency of the impressed voltage with whichย  the inductive reactance is equal to the capacitive reactance in magnitude.

A.ย  50 Hz

B.ย  51 Hz

C.ย  52 Hz

D.ย  none of these

Solution:

459.ย  EE Board Exam April 1989

A coil has a resistance of 50 ohms and a reactance of 100 ohms, is shunted by a capacitor, which has practically no losses. What must be the reactance of the capacitor in order that the voltage across the coil is in phase with the total current supplied to the parallel combination?

A.ย  120 ohms

B.ย  127 ohms

C.ย  125 ohms

D.ย  132 ohms

Solution:

460.ย  EE Board Exam April 1982

Three impedances Za, Zb and Zc are connected in parallel. If at 60 Hz, Za = j8, Zb = -j2 and Zc = 5 ohms, Solve for the frequency at resonance.

A.ย  30 Hz

B.ย  34 Hz

C.ย  36 Hz

D.ย  28 Hz

Solution:

461.ย  EE Board Exam April 1981

Aย  resistorย  R isย  connectedย  in parallelย  withย  aย  20-ohmย  inductiveย  reactive. The combination is then connected in seriesย  with a 5-ohm capacitive reactance. Solve the value of R at whichย  the power factor of the resultant impedance is unity.

A.ย  10.05 ohms

B.ย  9.15 ohms

C.ย  11.55 ohms

D.ย  10.73 ohms

Solution:

462.ย  EE Board Exam October 1998

A coil has a resistance of 50 ohms and a reactance of 70 ohms. A capacitor is connected in parallel to produceย  resonance. The source voltage is 120 V. What is the power drawn by the circuit?

A.ย  162 W

B.ย  97 W

C.ย  132 W

D.ย  52 W

Solution:

463.ย  EE Board Exam April 1995

A coil is supplied with 200 volts and takes a current (rms) of 2 amperes at 0.707 lagging. The quality factor (Q) of the coil is

A.ย  25

B.ย  1

C.ย  10

D.ย  100

Solution:

464.ย  EE Board Exam October 1998

In a series resonant RLC circuit, all of the following statements are correct EXCEPT one. Which one is this?

A.ย  The resonant frequency is dependent on the resistance of the circuit.

B.ย  The phase angle between the voltage and the current vectors is zero.

C.ย  The impedance is a minimum.

D.ย  The current is a maximum.

Solution:

465.ย  EE Board Exam April 1994, October 1993

The current in RLC series circuit at resonance is

A.ย  maximum

B.ย  zero

C.ย  minimum

D.ย  infinity

Solution:

466.ย  ECE Board Exam April 2001

Ignoring the capacitive effects, what is the impedance of a 100 mH coil (with an internal resistance of 45 ohms) in parallel with 4,700 ohms resistor at a frequency of 500 Hz?

A.ย  317 ohms

B.ย  237 0hms

C.ย  5014 ohms

D.ย  314 ohms

Solution:

467.ย  ECE Board Exam November 1996

____ frequency is reached when the capacitive and inductive reactance in a tuned circuit are equal.

A.ย  zero

B.ย  pulsating

C.ย  infinite

D.ย  resonant

Solution:

468.ย  ECE Board Exam November 1998

Findย  theย  Qย  ofย  aย  circuitย  whenย  theย  resonantย  frequencyย  isย  4.468ย  MHz,ย  the inductance is 47 microhenry and the resistance is 180 ohms parallel.

A.ย  0.136

B.ย  13.30

C.ย  0.00735

D.ย  7.35

Solution:

469.ย  ECE Board Exam November 2000

In an โIDEALโ resonant circuit, what is the relationship between the current and the impedance?

A.ย  current high, impedance low

B.ย  current low, impedance low

C.ย  current low, impedance high

D.ย  current high, impedance high

Solution:

470.ย  ECE Board Exam November 1997

What condition does resonance occurs in an electrical circuit?

A.ย  When the power factor is at minimum

B.ย  Whenย  theย  squareย  rootย  ofย  theย  sumย  ofย  theย  capacitiveย  andย  inductive reactances is to the resonant frequency

C.ย  When the inductive and capacitive reactances are equal

D.ย  none of these

Solution:

471.ย  ECE Board Exam November 2001

What is the relationship between frequency and the value of XC?

A.ย  frequency has no effect

B.ย  XC varies directly with frequency

C.ย  XC varies inversely with frequency

D.ย  XC varies indirectly with frequency

Solution:

472.ย  ECE Board Exam April 2001

When is the line current minimum in a parallel LC circuit?

B.ย  at the circuit frequency

C.ย  at the resonant frequency

D.ย  at the highest frequency

Solution:

473.ย  ECE Board Exam November 1999

Findย  theย  half-powerย  bandwidthย  ofย  aย  parallelย  resonantย  circuitย  whichย  hasย  a resonant frequency of 7.1 MHz and Q of 150.

A.ย  16.5 kHz

B.ย  211 kHz

C.ย  21.1 kHz

D.ย  47.3 kHz

Solution:

474.ย  ECE Board Exam November 1997

It is the term for the phenomena which occurs in an electrical circuit when the inductive reactance balances with the capacitive reactance.

A.ย  reactive equilibrium

B.ย  resonance

C.ย  reactive quiescence

D.ย  high Q

Solution:

475.ย  ECE Board Exam April 1998

What is the resonant frequency of a circuit when L of 25 microhenrys and C of 10 picofarads are in parallel?

A.ย  68.7 kHz

B.ย  10.1 kHz

C.ย  68.7 MHz

D.ย  10.1 MHz

Solution:

476.ย  ECE March 1996

What is the effect in terms of bandwidth when the Q of a single-tuned stage is doubled?

A.ย  halved

B.ย  the same

C.ย  doubled

D.ย  four times

Solution:

477.ย  ECE Board Exam November 1999

If you need an LC circuit to be resonant at 2,500 Hz and use a 150 mH coil, what should the capacitance value be?

A.ย  0.015 ฮผF

B.ย  0.15 ฮผF

C.ย  27 ฮผF

D.ย  0.027 ฮผF

Solution:

478.ย  ECE Board Exam April 1999

What is the resonant frequency of a circuitย  when L is 40 microhenrys and C is 6 picofarads are in series?

A.ย  6.63 MHz

B.ย  10.3 MHZ

C.ย  6.63 kHz

D.ย  10.3 kHz

Solution:

479.ย  ECE Board Exam April 1998

What is the resonant frequency of a circuit when L of 3 microhenrys and C of 40 picofarads are in series?

A.ย  14.5 MHz

B.ย  1.33 MHz

C.ย  1.33 kHz

D.ย  14.5 kHz

Solution:

480.ย  ECE Board Exam November 2001

____ refers to reactive power.

A.ย  power consumed in circuit Q

B.ย  power consumed in wire resistance in an inductor

C.ย  wattles, non-productive power

D.ย  power lost because of capacitor leakage

Solution:

481.ย  ECE Board Exam November 1998

How do you call the nature of a circuit during series resonance?

A.ย  unstable

B.ย  capacitive

C.ย  resistive

D.ย  inductive

Solution:

482.ย  ECE Board Exam April 1999

What is the resonant frequency of a circuit when L is 200 microhenrys and C is 10 picofarads are in series?

A.ย  7.96 MHz

B.ย  6 MHz

C.ย  3.56 MHz

D.ย  7.96 kHz

Solution:

483.ย  ECE Board Exam April 2000

Inย  aย  seriesย  resonantย  LCย  circuit,ย  whatย  isย  theย  impedanceย  atย  resonant frequency?

A.ย  Infinity

B.ย  Determined solely by the dc resistance

C.ย  The maximum impedance value

D.ย  Zero

Solution:

484.ย  ECE Board Exam April 1999

Whatย  isย  theย  characteristicย  ofย  theย  currentย  flowย  inย  aย  parallelย  R-L-Cย  circuitย  at resonance?

A.ย ย  The current circulating in the parallel elements is dc

B.ย  The current circulating in the parallel elements is zero

C.ย ย  The current circulating in the parallel elements is at a maximum

D.ย  The current circulating in the parallel elements is at a minimum

Solution:

485.ย  ECE Board Exam March 1996

Whatย  isย  theย  responsibleย  forย  theย  phenomenonย  whenย  voltagesย  across reactances in series can often be larger than the voltage applied to them?

A.ย  Capacitance

B.ย  Resistance

C.ย  Conductance

D.ย  Resonance

Solution:

486.ย  ECE Board Exam March 1996

Term used for resonance in an electrical circuit.

A.ย ย  The frequency at which power factor is at a minimum

B.ย  The frequency at which capacitive reactance equals inductive reactances

C.ย ย  The highest frequency that will pass current

D.ย  The lowest frequency that will pass current

Solution:

487.ย  ECE Board Exam November 1998

Ignoring any effects of dc resistance, what is the to tal reactance of a 250 mH coil in series with a 4.7 ฮผF capacitor at a signal frequency of 1000 Hz?

A.ย  1604 ฮฉ

B.ย  35 ฮฉ

C.ย  1536 ฮฉ

D.ย  1570 ฮฉ

Solution:

488.ย  ECE Board Exam November 1996

The _____ the Q of a circuit, the narrower is its bandwidth.

A.ย  Lower

C.ย  Higher

D.ย  Selective

Solution:

489.ย  ECE Board Exam March 1996

Findย  theย  half-powerย  bandwidthย  ofย  aย  resonantย  circuitย  whichย  hasย  aย  resonant frequency of 1.8 MHz and a Q of 95.

A.ย  58.7 kHz

B.ย  18.9 kHz

C.ย  189 Hz

D.ย  1.89 kHz

Solution:

490.ย  ECE Board Exam November 1998

What is the resonant frequency of a circuit when L is 5 microhenrys and C is 9 picofarads are in series?

A.ย  23.7 kHz

B.ย  3.54 kHz

C.ย  23.7 MHz

D.ย  3.54 MHz

Solution:

491.ย  ECE Board Exam April 1998

Findย  theย  half-powerย  bandwidthย  ofย  aย  parallelย  resonantย  circuitย  whichย  hasย  a resonant frequency of 3.6 MHz and a Q of 218.

A.ย  58.7 kHz

B.ย  606 kHz

C.ย  16.5 kHz

D.ย  47.3 kHz

Solution:

492.ย  ECE Board Exam November 1998

What is the resonant frequency of a circuit when L is 3 microhenrys and C is 40 picofarads are in parallel?

A.ย  14.5 kHz

B.ย  13.1 kHz

C.ย  14.5 MHz

D.ย  13.1 MHz

Solution:

493.ย  ECE Board Exam November 1998

What is the resonant frequency of a circuit when L is 15 microhenry and C is 5 picofarads are in series?

A.ย  2.12 kHz

B.ย  18.4 MHz

C.ย  18.4 kHz

D.ย  2.12 MHz

Solution:

494.ย  ECE Board Exam November 1998

What is the resonant frequency of a circuit when L is 2 microhenry and C is 15 picofarads are in series?

A.ย  29.1 MHz

B.ย  5.31 MHz

C.ย  29.1 kHz

D.ย  5.31 kHz

Solution:

495.ย  ECE Board Exam April 1998

Characteristic of the current flow in a series R-L-C circuit at resonance

A.ย  it is zero

B.ย  it is dc

C.ย  it is at a maximum

D.ย  it is at a minimum

Solution:

496.ย  ECE Board Exam April 2001

Whatย  isย  theย  termย  forย  theย  numberย  ofย  timesย  perย  secondย  thatย  aย  tankย  circuit energy is stored in the inductor of capacitor?

A.ย  Non-resonant frequency

C.ย  Circuit frequency

D.ย  Resonant frequency

Solution:

497.ย  ECE Board Exam November 1995

An LC circuit resonates at 2000 kHz, and has a Q of 100. Find the lower and upper cut-off frequencies.

A.ย  1950 kHz, 2050 kHz

B.ย  1990 kHz, 2010 kHz

C.ย  1980 kHz, 2020 kHz

D.ย  1900 kHz, 2100 kHz

Solution:

498.ย  ECE Board Exam November 1998

What is the resonant frequency of a circuit when L is 50 microhenrys and C is 10 picofarads are in parallel?

A.ย  3.18 kHz

B.ย  3.18 MHz

C.ย  7.12 MHz

D.ย  7.12 kHz

Solution:

499.ย  ECE Board Exam November 1999

What is the cause of a minimum Q on a single-tuned LC circuit?

A.ย  Decreased shunt resistor

B.ย  Decreased capacitance

C.ย  Increased shunt resistor

D.ย  Decreased series resistor

Solution:

500.ย  ECE Board Exam November 1998

____ is another term for quality factor or Q of the resonant circuit.

A.ย  Noise factor

B.ย  Noise figure

C.ย  White noise

D.ย  Figure of merit

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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