MCQ in AC Circuits Part 7 | REE Board Exam

This is the Multiple Choice Questions Part 7 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 7 of the Series

SERIES CIRCUITS

Choose the letter of the best answer in each questions.

⇐ MCQ in AC Circuits Part 6 | REE Board Exam

301.  A circuit component that opposes the change in circuit voltage is

A.  resistance

B.  capacitance

C.  inductance

D.  all of these

302.  Power loss in an electrical circuit can take place in

A.  inductance only

B.  capacitance only

C.  inductance and resistance

D.  resistance only

303.  A circuit of zero lagging power factor behaves as

A.  an inductive circuit

B.  a capacitive circuit

C.  R-L circuit

D.  R-C circuit

304.  In an R-L series circuit the power factor is

A.  leading

B.  lagging

C.  zero

D.  unity

305.  When a sinusoidal voltage is applied across an R-L series circuit having R = X_L, the phase angle will be

A.  90°

B.  45° lagging

C.  45° leading

D.  90° leading

306.  An  ac  source  having  voltage  e  =  110  sin  (ωt  +  π/3)  is  connected  in  an  ac circuit. If the current drawn from the circuit varies as i = 5 sin (ωt  –  π/3) the impedance of the circuit will be

A.  22 Ω

B.  16 Ω

C.  30.8   Ω

D.  none of these

307.  Which are of the following true of the circuit shown in the given figure?

1.  V_R =  100√2  V        2.  I = 2 A      3.  L = 0.25 H

Select the correct answer using the codes given below:

Codes:

A.  2 and 3

B.  1 and 2

C.  1 and 3

D.  1, 2 and 3

308.  The  R-L  circuit  of  the  figure  is  fed  from  a  constant  magnitude  variable frequency  sinusoidal  voltage  source  vin.  At  100  Hz,  the  R  and  L  element each has a voltage drop Vrms. If the  frequency of the source is changes to 50 Hz, then new voltage drop across R is

A.  √(5/8) Vrms

B.  √(2/3) Vrms

C.  √(8/5) Vrms

D.  √(3/2) Vrms

309. An ac source of 200 Vrms supplies active power of 600 W and reactive power of 800 VAR. The rms current drawn from the source is

A.  10 A

B.  5 A

C.  3.75 A

D.  2.5 A

310.  A square wave is fed to an R-C circuit. Then

A.  voltage across R is square and across C is not square

B.  voltage across C is square and across R is not square

C.  voltage across both R and C is square

D.  voltage across both R and C is not square

311.  The  voltage  phasor  of  a  circuit  is 10∠15° V  and  the  current  phasor  is 2∠-45° A. The active and reactive powers in the circuit are

A.  10 W and 17.32 VAR

B.  5 W and 8.66 VAR

C.  20 W and 60 VAR

D.  20√2 W and  10√2 VAR

312.  In a two-element series circuit, the applied voltage and resultant current are respectively, v(t) = 50 + 50 sin (5 x 10³ t) and i(t) = 11.2 sin (5 x 10³ t + 63.4°). The nature of the elements would be

A.  R-L

B.  R-C

C.  L-C

D.  neither R, nor L, nor C

313.  A  series  circuit  passive  elements  has  the  following  current  and  applied voltage: v = 200 sin (2,000t + 50°), i = 4 cos (2,000t + 13.2°). The circuit elements

A.  must be resistance and capacitance

B.  must be resistance and inductance

C.  must be inductance, capacitance and resistance

D.  could  be  either  resistance  and  capacitance  or  resistance,  inductance and capacitance

314.  A two terminal black box contains one of the R-L-C elements. The black box is connected to a 220 V ac supply. The current through the source is I. When a capacitance of 0.1 F is inserted in series between the source and the box, the current through the source is 2I. The element is

A.  a resistance

B.  an inductance

C.  a capacitance

D.  it is not possible to determine the element

315.  In the following circuit, i(t) under steady state is

A.  zero

B.  5

C.  7.07 sin t

D.  7.07 sin (t – 45°)

316.  The source in the circuit is a sinusoidal source. The supply voltages across various elements are marked in the figure. The input voltage is

A.  10 V

B.  5 V

C.  27 V

D.  24 V

317.  In the circuit shown in the given figure, if the power consumed by the 5 Ω resistor is 10 W, then the pf of the circuit is

A.  0.8

B.  0.6

C.  0.5

D.  zero

318.  In  an  RL  circuit,  supplied  from  an  ac  source,  the  reactive  power  is proportional to the

A.  the average energy stored in the electric field

B.  the average energy stored in the magnetic field

C.  sum of the average energy stored in the electric field and that stored in the magnetic field

D.  difference  of  the  average  energy  stored  in  the  electric  field  and  that stored in the magnetic field

319.  If a series RLC circuit excited by a voltage e = E sin ωt when LC < 1/ω²

A.  current lags behind the applied voltage

B.  current leads the applied voltage

C.  current is in phase with the applied voltage

D.  voltage across L and C are equal

320.  The current in the circuit shown is

A.  5 A

B.  10 A

C.  15 A

D.  25 A

321.  In the case of the R-L-C circuit shown in the given figure, the voltage across the R, L and C would be respectively

A.  12 V, 16 V and 7 V or 25 V

B.  16 V, 12 V and 7 V or 25 V

C.  7 V, 16 V and 12 V

D.  16 V, 12 V and 25 V

322.  Consider the following statements regarding the circuit shown in the figure.

If the power consumed by 5 Ω resistor is 10 W then

1.  |I| = √2  A

2.  the total impedance of the circuit is 5 Ω

3.  cos θ = 0.866

Which of these statements is correct?

A.  1 and 3

B.  2 and 3

C.  1 and 2

D.  1, 2 and 3

323.  In an ac circuit if voltage V = (a + jb) and current I = (c + jd), then the power is given by

A.  ac + ad

B.  ac + bd

C.  bc – ad

D.  bc + ad

324.  The reactive power drawn from the source in the network in the given figure is

A.  300 VAR

B.  200 VAR

C.  100 VAR

D.  zero

325.  A  series  R-L-C  circuit,  consisting  of  R  =  10  Ω,  X_L  =  20  Ω,  X_C  =  20  Ω  is connected  across  an ac supply  of  100  V  (rms).  The  magnitude  and  phase angle (with reference to supply voltage) of the voltage across the inductive coil are respectively

A.  100 V, 90°

B.  100 V, -90°

C.  200 V, -90°

D.  200 V, 90°

326.  For a capacitor in a sine wave ac circuit

A.  v_C lags i_C by 90°

B.  i_C leads v_C by 90°

C.  i_C and v_C have the same frequency

D.  all of these

327.  In a series RC circuit,

A.  V_C leads V_R by 90°

B.  V_C and I are in phase

C.  V_C lags V_R by 90°

D.  both B and C

328.  In a series RC circuit,

A.  V_C and V_R are in phase

B.  V_T and I are always in phase

C.  V_R and I are in phase

D.  V_R leads I by 90°

329.  When the frequency of the applied voltage increases in a series RC circuit

A.  the phase angle, θ_T, becomes more negative

B.  Z_T increases

C.  Z_T decreases

D.  both A and B

330.  Inductive reactance, X_L

A.  applies only to non-sinusoidal waveforms or dc

B.  applies only to sine waves

C.  applies to either sinusoidal or non-sinusoidal waveforms

D.  is inversely proportional to frequency

331.  For an inductor in a sine wave ac circuit

A.  V_T leads i_L by 90°

B.  V_T lags i_L by 90°

C.  V_T and i_L are in phase

D.  none of these

332.  In a series RL circuit,

A.  V_T lags V_R by 90°

B.  V_T leads V_R by 90°

C.  V_R and I are in phase

D.  both B and C

333.  In a series RL circuit where X_L = R, the phase angle, θ_Z, is

A.  -45°

B.  0°

C.  90°

D.  45°

334.  In an ac circuit with only series resistances

A.  V_T and I are in phase

B.  R_T =R1 + R2 + R3 + … + etc.

C.  each voltage drop is in phase with the series current

D.  all of these

335.  The unit of apparent power is the

A.  volt-ampere (VA)

B.  watt (W)

C.  volt-ampere-reactive (VAR)

D.  joule (J)

336.  In an ac circuit with only series capacitors

A.  V_T leads I by 90°

B.  V_T lags I by 90°

C.  each capacitor voltage drop leads I by 90°

D.  both A and C

337.  The unit of real power is the

A.  watt (W)

B.  volt-ampere (VA)

C.  joule (J)

D.  volt-ampere-reactive (VAR)

338.  In a series RLC circuit

A.  X_L and X_C are 180° out of phase

B.  I_L and I_C are 180° out of phase

C.  X_L and X_C are 90° out of phase

D.  X_L and X_C are in phase

339.  The power factor of an ordinary electric bulb is

A.  zero

B.  unity

C.  slightly more than unity

D.  slightly less than unity

340.  The power factor of an ac circuit is equal to

A.  cosine of the phase angle

B.  sine of the phase angle

C.  unity for a resistive circuit

D.  unity for a reactive circuit

341.  If f(t) = sin t + sin √2 t is passing through R = 1 ohm, what is the power dissipated in 1 ohm resistor?

A.  1 W

B.  2 W

C.  since f(t) in non-periodic, not possible to find power

D.  none of these

C.  PARALLEL CIRCUITS

342.  EE Board Exam October 1981

A circuit consists of X_L = j5 ohms, X_C = -j5 ohms and R = 5 ohms all are connected in parallel. Find the equivalent impedance.

A.  5.5 Ω

B.  5.0 Ω

C.  4.8 Ω

D.  5.2 Ω

343.  EE Board Exam October 1985

Given: Z₁  =  -j2.5 ohms; Z₂  = j4 ohms; Z₃  = 5 ohms; Z₄  = 1 + j5 ohms. If the four impedances are connected in parallel, find the equivalent impedance in ohms.

A.  4.1 + j0.72

B.  4.3 + j0.45

C.  4.2 + j0.35

D.  4.0 + j0.97

344.  EE Board Exam April 1984, April 1987

Three impedances Z_a = 3 + j4 ohms, Z_b = 4 –  j4 ohms  and Z_c = j3 ohms are connected in parallel. Solve for the pf of the combination.

A.  0.653 leading

B.  0.554 lagging

C.  0.503 leading

D.  0.620 lagging

345.  EE Board Exam October 1993

A pure capacitance of 530.515 x 10^-6 farad and an inductance of 530.515 x 10^-4 Henry  are  connected  in parallel  across  an ac  power  source.  Solve  for the resultant impedance assuming that the frequency is 30 Hz.

A.  10 Ω

B.  infinite

C.  zero

D.  undefined

346.  REE Board Exam March 1998

A coil of a 50-ohm resistance and of 150 mH inductance is connected in parallel with a 50 μF capacitor. What is the power factor of the circuit?

A.  80%

B.  50%

C.  70%

D.  60%

347.  EE Board Exam April 1982

Three impedances Za, Zb and Zc are connected in parallel. If at 60 Hz, Z_a = j8, Z_b = -j2 and Z_c = 5 ohms. Solve for the resultant power factor.

A.  0.471 lagging

B.  0.471 leading

C.  0.573 lagging

D.  0.573 leading

348.  REE Board Exam October 1997

A resistor of 50 ohms and an impedance of 100 + j50 ohms are connected in parallel across a 220 volts supply. What is the power factor of the load?

A.  96%

B.  99%

C.  98%

D.  95%

349.  EE Board Exam October 1992

A capacitor of 3.18 microfarads is connected in parallel with a resistance of 2,000  ohms.  The  combination  is  further  connected  in  series  with  an inductance of 795 mH and  resistance of 100 ohms across a supply given by e = 400 sin wt + 80 sin (3wt + 60°). Assume w = 314 radians/sec. Determine the power dissipated.

A.  74.66 W

B.  78.05 W

C.  80.28 W

D.  75.66 W

350.  EE Board Exam October 1992

A capacitor of 3.18 microfarads is  connected in parallel with a resistance of 2,000  ohms.  The  combination  is  further  connected  in  series  with  an inductance of 795 mH and resistance of 100 ohms across a supply given by e = 400 sin wt + 80 sin (3wt + 60°). Assume w = 314 radians/sec. Determine the circuit power factor.

A.  0.702

B.  0.650

C.  0.633

D.  0.612

⇒ MCQ in AC Circuits Part 8 | REE Board Exam

Questions and Answers in AC Circuits

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