MCQ in AC Circuits Part 5 | REE Board Exam

This is the Multiple Choice Questions Part 5 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 5 of the Series

SERIES CIRCUITS

Choose the letter of the best answer in each questions.

⇐ MCQ in AC Circuits Part 4 | REE Board Exam

201.  REE Board Exam September 2001

In laboratory experiment, the impedance of the coil was obtained at 60 Hz and 30 Hz. These are 75.48 ohms and 57.44 ohms respectively. What is the inductance of the coil?

A.  150 mH

B.  182.5 mH

C.  42.5 mH

D.  2.1 mH

202.  REE Board Exam September 2002

A  10  ohms  inductive  resistor  is  connected  in  series  with  an  unknown capacitance. At 60 Hz the impedance of the circuit is 10 + j11.72 ohms. At 30 Hz  the  impedance  of  the  circuit  is  10  –  j5  ohms.  What  is  the  value  of  L  in millihenrys?

A.  50

B.  500

C.  100

D.  250

203.  REE Board Exam April 1995

An impedance coil takes 10 A and absorbs 250 W when connected across a 220 V, 60 Hz source. What power will it absorb when connected across 110 V, 25 Hz mains?

A.  539 W

B.  239 W

C.  439 W

D.  339 W

204.  EE Board Exam October 1984

An industrial coil has a  resistance of 32 ohms and a reactance of 24 ohms and rated 440 volts at 60 Hz. A factory will connect the coil to a 440 V, 50 Hz supply. How much percentage over-current will the coil suffer?

A.  5%

B.  10%

C.  6%

D.  8%

205.  REE Board Exam March 1998

A 25  Ω  resistor connected in series with a coil of 50  Ω  resistance and 150 mH inductance. What is the power factor of the circuit?

A.  85%

B.  80%

C.  90%

D.  75%

206.  REE Board Exam April 1997

A  current  of  2.5  A  flows  through  a  series  circuit  consisting  of  a  100  ohm resistor and an unknown capacitor across a source of 460 V, 50 Hz. What is the value of the capacitive reactance?

A.  X_C = 91.86 Ω

B.  X_C = 39.19 Ω

C.  X_C = 154.45 Ω

D.  X_C = 184 Ω

207.  REE Board Exam October 1998

The  ohmic  resistance  of  a  large  magnetic  contactor  is  measured  to  be  20 ohms. A 230 V is impressed on the contractor and the current is taken as 3.2 A. Neglecting core loss, determine the inductance of the contractor in mH?

A.  261

B.  315

C.  183

D.  251

208.  REE Board Exam March 1998

A  load  of  20  +  j35  Ω  is  connected  across  a  220  V  source.  Determine  the power factor and the VARS.

A.  49.6%, 1042 vars

B.  52.2%, 1023 vars

C.  85.3%, 975 vars

D.  42.3%, 1087 vars

209.  EE Board Exam October 1990

Find  the  total  impedance  in  rectangular  form  for  the  following  three  series impedances:

12∠10° ohm,  25∠15° ohm, 34∠26° ohm.

A.  66.52 + j23.46 Ω

B.  68.34 + j20.54 Ω

C.  74.31 + j21.56 Ω

D.  67.70 + j22.04 Ω

210.  REE Board Exam October 1997

An impedance draws a current i = 10 cos (ωt – 30°) A from a voltage, v = 220 sin (ωt + 30°) V. What is the impedance?

A.  15.6 – j15.6 Ω

B.  15.6 + j15.6 Ω

C.  19.1 – j11.1 Ω

D.  11.0 + j19.1 Ω

211.  EE Board Exam April 1990

A series resistance-capacitance (R-C) circuit is connected to a 230 volt 60 cycle source. If the power taken by the circuit  is 4,800 watts and the voltage drop  across  the  resistor  is  115  volts,  calculate  the  capacitance  of  the capacitor.

A.  540 μF

B.  530 μF

C.  556 μF

D.  503 μF

212.  REE Board Exam March 1998

A 50 μF and 100 μF capacitors are connected in series and across a 100 sin (ωt + 30°) voltage. Write the equation of the current.

A.  1.26 sin (ωt + 120°) A

B.  1.26 sin (ωt + 90°) A

C.  5.65 sin (ωt + 120°) A

D.  5.56 sin (ωt + 90°) A

213.  EE Board Exam April 1993

A 100∠0° V,  120  Hz  generator  and  a  80∠0° V,  60  Hz  generator  are connected  in  series  with  a  60  V  battery  and  a  coil.  The  resistance  and inductance of the coil are 3  Ω and 2.65 mH, respectively. Determine the rms current of the coil.

A.  42.54 A

B.  44.24 A

C.  43.55 A

D.  40.44 A

214.  REE Board Exam October 1996

A series circuit composed of 100-ohm resistor and a 20-microfarad capacitor connected  across  a  240-V,  60  Hz  line.  Which  of  the  following  answers  is WRONG?

A.  the impedance of the circuit is 167 ohms

B.  angle between the current and the voltage vectors is 53.1 degrees

C.  the resulting current is 0.723 ampere

D.  the voltage across the resistance is 144.6 volts

215.  REE Board Exam April 1994

A capacitance is connected to a 115-V, 25 Hz mains and takes 5 A. What current  will  it  take  when  the  capacitance  and  the  frequency  are  both doubled?

A.  2.5 A

B.  5 A

C.  20 A

D.  10 A

216.  REE Board Exam October 1996

A capacitor is rated 100 kVAR, 380 V, 50 Hz, What will its rating be at 60 Hz, 220 V?

A.  50 kVAR

B.  40 kVAR

C.  90.9 kVAR

D.  57.7 kVAR

217.  REE Board Exam October 1992

A resistor and a capacitor are connected in series across a supply of 250 V. When the supply frequency is 50 Hz the current in the circuit is 5 A. When the  supply  frequency  is  60  Hz,  the  current  is  5.8  A.  Find  the  value  of  the capacitance.

A.  58.3 μF

B.  69.1 μF

C.  60.2 μF

D.  70.2 μF

218.  EE Board Exam October 1993

A  series  circuit  composed  of  a  0.2  Henry  inductor  and  a  74-microfarad capacitor  is  connected  to  a  60  V  variable  frequency  source.  At  what frequency is the current be 4 amperes with a lagging power factor?

A.  50 Hz

B.  51 Hz

C.  48 Hz

D.  49 Hz

219.  REE Board Exam October 1998

The maximum instantaneous voltage and current output of an alternator are 300 V and 20 A, respectively. What is the power output in watts if the voltage leads the current by 30°?

A.  2598

B.  3000

C.  5196

D.  6000

220.  REE Board Exam October 1998

A 50-microfarad is connected in series with a coil having 50 ohms resistance and 150 mH inductance. The source voltage is 100 sin (ωt – 120°) V. What is the maximum power?

A.  199 watts

B.  147 watts

C.  212 watts

D.  165 watts

221.  REE Board Exam October 1997

An impedance draws a current i = 10 cos (ωt –  30°) A from a voltage v = 220 sin ωt. What is the maximum power?

A.  2200 watts

B.  1100 watts

C.  190.5 watts

D.  1320 watts

222.  REE Board Exam April 1995

An incandescent lamp load generally considered to be made up of resistors take 4.8 kW from a 120 V ac source. The instantaneous maximum value of power is

A.  4800 W

B.  2400 W

C.  480 W

D.  9600 W

223.  ECE Board Exam November 1998

The  term  used  for  an  out-of-phase,  non-productive  power  associated  with inductors and capacitors?

A.  peak envelope power

B.  effective power

C.  true power

D.  reactive power

224.  ECE Board Exam November 2001

What is the capacitive reactance of a 33 microfarad capacitor at 6500 Hz?

A.  7.4 0hms

B.  96 0hms

C.  0.74 ohms

D.  1122 ohms

225.  ECE Board Exam November 1999

The power dissipated across the resistance in an AC circuit.

A.  true power

B.  real power

C.  reactive power

D.  apparent power

226.  ECE Board Exam April 2000

What is the capacitive reactance of a 33 microfarad capacitor at 500 Hz?

A.  1,000,000 ohms

B.  144 ohms

C.  0 ohms

D.  9.55 ohms

227.  ECE Board Exam November 1998

What is the reactance of a 25 mH coil at 600 Hz?

A.  0.011 ohm

B.  94,000 ohms

C.  785 ohms

D.  94 ohms

228.  ECE Board Exam April 1999

Ignoring capacitance effects, what is the impedance of a 250 mH coil with an internal resistance of 55 ohms at 60 Hz?

A.  149.2 ohms

B.  109 ohms

C.  94.2 ohms

D.  10,900 ohms

229.  ECE Board Exam November 1999

Ignoring any inductive effects, what is the impedance of RC series capacitor made  up  of  a  56  kilo  ohms  resistor  and  a  0.033  μF  capacitor  at  a  signal frequency of 450 Hz?

A.  66,730 Ω

B.  57,019 Ω

C.  10,730 Ω

D.  45,270 Ω

230.  ECE Board Exam April 2000

Assuming  an  ideal  capacitor,  with  no  leakage,  what  is  the  capacitive reactance of 10 microfarad capacitance of DC (0 Hz)?

A.  0 ohms

B.  16000 ohms

C.  1,000,000 ohms

D.  infinite capacitive reactance

231.  ECE Board Exam April 1998

The impedance in the study of electronics is  represented by resistance and _____

A.  Reactance

B.  Capacitance

C.  Inductance

D.  Inductance and capacitance

232.  ECE Board Exam November 2000

One of the following satisfies the condition of Ohm’s Law

A.  Application to metals which heated up due to flow of current over them

B.  Application  to  AC  circuit  having  its  impedance  used  in  place  of resistance

C.  Application to semiconductor

D.  Application to vacuum radio valves

233.  The effective voltage across a circuit element is (20 + j10) and the effective current through the element is 4  – j3 A. Calculate the true and reactive power taken by the element.

A.  50 watts & 100 vars lagging

B.  50 watts & 100 vars leading

C.  110 watts & 20 vars lagging

D.  110 watts & 20 vars leading

234.  The voltage across a given circuit  is 75 + j50 V. What is the power supplied to the circuit if the current through it is (8 – j5) A?

A.  850 W

B.  550 W

C.  750 W

D.  350 W

235.  Find average power in a resistance R = 10 ohms if the current in series form is i = 10 sin ωt + 5 sin 3ωt + 2 sin 5ωt amperes.

A.  65.4 watts

B.  645 watts

C.  546 watts

D.  5.46 watts

236.  Across  a  230-V,  60  Hz  power  supply  is  a  15-ohm  non-inductive  resistor. What is the equation of the voltage and resulting current?

A.  e = 398.4 sin 60t and i = 21.6 sin 60t

B.  e = 325.5 sin 377t and i = 21.6 sin 377t

C.   e = 230 sin 377t and i = 15.3 sin 377t

D.  e = 230 sin 120t and i = 15.3 sin 120t

237.  A resistor R and a capacitor C are connected in series across a 100 V, 60 cycle source. The reading of an ammeter connected in the circuit is  2 A and the reading of a voltmeter connected across the capacitor is 80 V. Calculate the values of R and C.

A.  66 Ω & 30 μF

B.  30 Ω & 60 μF

C.  30 Ω & 66 μF

D.  36 Ω & 60 μF

238.  A series circuit consisting of a 66.2 μF capacitor and a variable resistor. For what  two  values  of  resistance  will  the  power  taken  by  the  circuit  be  172.8 watts, if the impressed 60-cycle emf is 120 volts?

A.  85.33 & 3.33 ohms

B.  53.33 & 30 ohms

C.  5.33 & 3.0 ohms

D.  83.33 & 5.33 ohms

239.  A  series  circuit  composed  of  0.2  H  inductor  and  a  74  μF  capacitor  is connected  to a  60  V  variable  frequency  source.  At  what  frequency  will the current be 4 A with lagging power factor?

A.  47.767 Hz

B.  74.68 Hz

C.  60 Hz

D.  50 Hz

240.  A  30  ohm  resistor  is  connected  in  parallel  with  an  inductor  of  inductive reactance X_L. The combination is then connected in series with a capacitor of reactance X_C. What is the value of X_L and X_C if the total impedance is 1.92 ohms?

A.  7.84 and 7.34

B.  47.4 and 47.3

C.  44.8 and 84.21

D.  84.7 and 34.7

241.  An impedance of 100 Ω resistance and an unknown inductance is connected across the capacitor. The resulting impedance is a pure resistance of 500  Ω if ω = 10⁵ rad/sec. Calculate the values of inductor and capacitor.

A.  1 μF & 2 mH

B.  5 μF & 1 mH

C.  7 μF & 3 mH

D.  0.04 μF & 2 mH

242.  The voltage across the resistor, inductor and capacitor in series is 60 V, 90 V and 10 V respectively. What is the voltage across this circuit?

A.  160 V

B.  140 V

C.  100 V

D.  50 V

243.  The open circuit voltage of  an alternator is 127 V and its internal impedance is 10∠10° Ω. Find the voltage across a load of 30∠-30° Ω.

A.  100∠-9.7° V

B.  97∠-10° V

C.  79∠-10° V

D.  100∠-7.9° V

244.  The maximum values of alternating voltage and current are 400 V and 20 A, respectively. In a circuit connected to 50 Hz supply and these quantities are sinusoidal. The instantaneous values of voltage and current are 283 V and 10 A respectively at t = 0 both increasing positively. What is power factor of the circuit?

A.  0.707

B.  0.83

C.  0.85

D.  0.965

245.  The potential difference measured across a coil is 4.5 V, when it carries a direct current of 9 A. The same coil when carries an alternating current of 9 A at 25 Hz, the potential difference is 24 V. Find the power when it is  supplied by 50 V, 50 Hz supply.

A.  45 W

B.  54 W

C.  63 W

D.  30 W

246.  Two  coils  A  and  B are connected  in  series  across  a 240  V,  50  Hz  supply. The resistance of A is 5  Ω  and the inductance of B is 0.015 H. If the input from the supply is 3 kW and 2 kVAR, find the inductance of A and resistance of B.

A.  0.0132 H & 8.3 Ω

B.  0.215 H & 3.8 Ω

C.  0.026 H & 12 Ω

D.  0.031 H & 5.3 Ω

247.  A  current  of  5  A  flows  through  a  non-inductive  resistance  in  series  with  a choking  coil  when  supplied  at  250  V,  50  Hz.  If  the  voltage  across  the resistance  is  120  V  and  across  the  coil  is  200  V,  calculate  the  power absorbed by the coil in watts.

A.  168.75 W

B.  137.5 W

C.  51.37 W

D.  75.31 W

248.  A single phase, 7.46 kW motor is supplied from a 400 V, 50 Hz AC mains. If its  efficiency  is  85%  and  the  power  factor  is  0.8  lagging,  find  the  reactive component of the input current.

A.  16.46 A

B.  21.95 A

C.  27.43 A

D.  21 A

249.  A series RLC circuit consists of 20 ohms resistance, 0.2 H inductance and an unknown capacitance. What is the value of the  capacitance if the circuit has a leading angle of 45° at 60 Hz?

A.  35.18 μF

B.  47.9 μF

C.  27.8 μF

D.  30.7 μF

250.  A 3 HP, 120 V, 60 Hz induction motor operating at 80% efficiency and 0.866 lagging  power  factor  is  to  be  used  temporarily  with  240  V,  60  Hz  source. What  resistance  in  series  with  the  motor  will  be  required  for  the  motor  to have 120 V across its terminals at full load?

A.  6.68 Ω

B.  4.77 Ω

C.  13.76 Ω

D.  9.54 Ω

⇒ MCQ in AC Circuits Part 5 | REE Board Exam

Questions and Answers in AC Circuits

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