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.**

โ MCQ in AC Circuits Part 4 | REE Board Exam

201.ย REE Board Exam September 2001

Inย laboratory experiment, the impedance of the coil wasย obtained atย 60 Hz and 30 Hz. These are 75.48 ohms and 57.44 ohms respectively. What is the inductance of the coil?

A.ย 150 mH

B.ย 182.5 mH

C.ย 42.5 mH

D.ย 2.1 mH

202.ย REE Board Exam September 2002

Aย 10ย ohmsย inductiveย resistorย isย connectedย inย seriesย withย anย unknown capacitance. At 60 Hz the impedance of the circuit is 10 + j11.72 ohms. At 30 Hzย theย impedanceย ofย theย circuitย isย 10ย โย j5ย ohms.ย Whatย isย theย valueย ofย Lย in millihenrys?

A.ย 50

B.ย 500

C.ย 100

D.ย 250

Answer: **Option A**

Solution:

203.ย 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.ย 539 W

B.ย 239 W

C.ย 439 W

D.ย 339 W

Answer: **Option D
**

Solution:

204.ย EE Board Exam October 1984

An industrial coil has aย 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.ย 5%

B.ย 10%

C.ย 6%

D.ย 8%

Answer: **Option C**

Solution:

205.ย REE Board Exam March 1998

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

A.ย 85%

B.ย 80%

C.ย 90%

D.ย 75%

Answer: **Option B**

Solution:

206.ย REE Board Exam April 1997

Aย currentย ofย 2.5ย Aย flowsย throughย aย seriesย circuitย consistingย ofย aย 100ย ohm resistor and an unknown capacitor across a source of 460 V, 50 Hz. What is the value of the capacitive reactance?

A.ย X_{C} = 91.86 ฮฉ

B.ย X_{C} = 39.19 ฮฉ

C.ย X_{C} = 154.45 ฮฉ

D.ย X_{C} = 184 ฮฉ

Answer: **Option C**

Solution:

207.ย REE Board Exam October 1998

Theย ohmicย resistanceย ofย aย largeย magneticย contactorย isย measuredย toย beย 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.ย 261

B.ย 315

C.ย 183

D.ย 251

Answer: **Option C**

Solution:

208.ย REE Board Exam March 1998

Aย loadย ofย 20ย +ย j35ย ฮฉย isย connectedย acrossย aย 220ย Vย source.ย Determineย the power factor and the VARS.

A.ย 49.6%, 1042 vars

B.ย 52.2%, 1023 vars

C.ย 85.3%, 975 vars

D.ย 42.3%, 1087 vars

Answer: **Option A**

Solution:

209.ย EE Board Exam October 1990

Findย theย totalย impedanceย inย rectangularย formย forย theย followingย threeย series impedances:

12โ 10ยฐ ohm,ย 25โ 15ยฐ ohm, 34โ 26ยฐ ohm.

A.ย 66.52 + j23.46 ฮฉ

B.ย 68.34 + j20.54 ฮฉ

C.ย 74.31 + j21.56 ฮฉ

D.ย 67.70 + j22.04 ฮฉ

Answer: **Option A**

Solution:

210.ย REE Board Exam October 1997

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

A.ย 15.6 โ j15.6 ฮฉ

B.ย 15.6 + j15.6 ฮฉ

C.ย 19.1 โ j11.1 ฮฉ

D.ย 11.0 + j19.1 ฮฉ

Answer: **Option C**

Solution:

211.ย 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 circuitย is 4,800 watts and the voltage dropย acrossย theย resistorย isย 115ย volts,ย calculateย theย capacitanceย ofย the capacitor.

A.ย 540 ฮผF

B.ย 530 ฮผF

C.ย 556 ฮผF

D.ย 503 ฮผF

Answer: **Option C**

Solution:

212.ย REE Board Exam March 1998

A 50 ฮผF and 100 ฮผF capacitors are connected in series and across a 100 sin (ฯt + 30ยฐ) voltage. Write the equation of the current.

A.ย 1.26 sin (ฯt + 120ยฐ) A

B.ย 1.26 sin (ฯt + 90ยฐ) A

C.ย 5.65 sin (ฯt + 120ยฐ) A

D.ย 5.56 sin (ฯt + 90ยฐ) A

Answer: **Option A**

Solution:

213.ย EE Board Exam April 1993

A 100โ 0ยฐ V,ย 120ย Hzย generatorย andย aย 80โ 0ยฐ V,ย 60ย Hzย generatorย are connectedย inย seriesย withย aย 60ย Vย batteryย andย aย coil.ย Theย resistanceย and inductance of the coil are 3ย ฮฉ and 2.65 mH, respectively. Determine the rms current of the coil.

A.ย 42.54 A

B.ย 44.24 A

C.ย 43.55 A

D.ย 40.44 A

Answer: **Option A**

Solution:

214.ย REE Board Exam October 1996

A series circuit composed of 100-ohm resistor and a 20-microfarad capacitor connectedย acrossย aย 240-V,ย 60ย Hzย line.ย Whichย ofย theย followingย answersย is WRONG?

A.ย the impedance of the circuit is 167 ohms

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

C.ย the resulting current is 0.723 ampere

D.ย the voltage across the resistance is 144.6 volts

Answer: **Option C**

Solution:

215.ย REE Board Exam April 1994

A capacitance is connected to a 115-V, 25 Hz mains and takes 5 A. What currentย willย itย takeย whenย theย capacitanceย andย theย frequencyย areย both doubled?

A.ย 2.5 A

B.ย 5 A

C.ย 20 A

D.ย 10 A

Answer: **Option C**

Solution:

216.ย 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.ย 50 kVAR

B.ย 40 kVAR

C.ย 90.9 kVAR

D.ย 57.7 kVAR

Answer: **Option B**

Solution:

217.ย 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 theย supplyย frequencyย isย 60ย Hz,ย theย currentย isย 5.8ย A.ย Findย theย valueย ofย the capacitance.

A.ย 58.3 ฮผF

B.ย 69.1 ฮผF

C.ย 60.2 ฮผF

D.ย 70.2 ฮผF

Answer: **Option B**

Solution:

218.ย EE Board Exam October 1993

Aย seriesย circuitย composedย ofย aย 0.2ย Henryย inductorย andย aย 74-microfarad capacitorย isย connectedย toย aย 60ย Vย variableย frequencyย source.ย Atย what frequency is the current be 4 amperes with a lagging power factor?

A.ย 50 Hz

B.ย 51 Hz

C.ย 48 Hz

D.ย 49 Hz

Answer: **Option C**

Solution:

219.ย 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 30ยฐ?

A.ย 2598

B.ย 3000

C.ย 5196

D.ย 6000

Answer: **Option A**

Solution:

220.ย 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 (ฯt โ 120ยฐ) V. What is the maximum power?

A.ย 199 watts

B.ย 147 watts

C.ย 212 watts

D.ย 165 watts

Answer: **Option A**

Solution:

221.ย REE Board Exam October 1997

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

A.ย 2200 watts

B.ย 1100 watts

C.ย 190.5 watts

D.ย 1320 watts

Answer: **Option B**

Solution:

222.ย 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.ย 4800 W

B.ย 2400 W

C.ย 480 W

D.ย 9600 W

Answer: **Option D**

Solution:

223.ย ECE Board Exam November 1998

Theย termย usedย forย anย out-of-phase,ย non-productiveย powerย associatedย with inductors and capacitors?

A.ย peak envelope power

B.ย effective power

C.ย true power

D.ย reactive power

Answer: **Option D**

Solution:

224.ย ECE Board Exam November 2001

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

A.ย 7.4 0hms

B.ย 96 0hms

C.ย 0.74 ohms

D.ย 1122 ohms

Answer: **Option C**

Solution:

225.ย ECE Board Exam November 1999

The power dissipated across the resistance in an AC circuit.

A.ย true power

B.ย real power

C.ย reactive power

D.ย apparent power

Answer: **Option B**

Solution:

226.ย ECE Board Exam April 2000

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

A.ย 1,000,000 ohms

B.ย 144 ohms

C.ย 0 ohms

D.ย 9.55 ohms

Answer: **Option D**

Solution:

227.ย ECE Board Exam November 1998

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

A.ย 0.011 ohm

B.ย 94,000 ohms

C.ย 785 ohms

D.ย 94 ohms

Answer: **Option D**

Solution:

228.ย 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.ย 149.2 ohms

B.ย 109 ohms

C.ย 94.2 ohms

D.ย 10,900 ohms

Answer: **Option B**

Solution:

229.ย ECE Board Exam November 1999

Ignoring any inductive effects, what is the impedance of RC series capacitor madeย upย ofย aย 56ย kiloย ohmsย resistorย andย aย 0.033ย ฮผFย capacitorย atย aย signal frequency of 450 Hz?

A.ย 66,730 ฮฉ

B.ย 57,019 ฮฉ

C.ย 10,730 ฮฉ

D.ย 45,270 ฮฉ

Answer: **Option C**

Solution:

230.ย ECE Board Exam April 2000

Assumingย anย idealย capacitor,ย withย noย leakage,ย whatย isย theย capacitive reactance of 10 microfarad capacitance of DC (0 Hz)?

A.ย 0 ohms

B.ย 16000 ohms

C.ย 1,000,000 ohms

D.ย infinite capacitive reactance

Answer: **Option D**

Solution:

231.ย ECE Board Exam April 1998

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

A.ย Reactance

B.ย Capacitance

C.ย Inductance

D.ย Inductance and capacitance

Answer: **Option A**

Solution:

232.ย ECE Board Exam November 2000

One of the following satisfies the condition of Ohmโs Law

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

B.ย Applicationย toย ACย circuitย havingย itsย impedanceย usedย inย placeย of resistance

C.ย Application to semiconductor

D.ย Application to vacuum radio valves

Answer: **Option B**

Solution:

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

A.ย 50 watts & 100 vars lagging

B.ย 50 watts & 100 vars leading

C.ย 110 watts & 20 vars lagging

D.ย 110 watts & 20 vars leading

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

A.ย 850 W

B.ย 550 W

C.ย 750 W

D.ย 350 W

Answer: **Option D**

Solution:

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

A.ย 65.4 watts

B.ย 645 watts

C.ย 546 watts

D.ย 5.46 watts

Answer: **Option B**

Solution:

236.ย Acrossย aย 230-V,ย 60ย Hzย powerย supplyย isย aย 15-ohmย non-inductiveย resistor. What is the equation of the voltage and resulting current?

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

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

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

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

Answer: **Option B**

Solution:

237.ย 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 isย 2 A and the reading of a voltmeter connected across the capacitor is 80 V. Calculate the values of R and C.

A.ย 66 ฮฉ & 30 ฮผF

B.ย 30 ฮฉ & 60 ฮผF

C.ย 30 ฮฉ & 66 ฮผF

D.ย 36 ฮฉ & 60 ฮผF

Answer: **Option C**

Solution:

238.ย A series circuit consisting of a 66.2 ฮผF capacitor and a variable resistor. For whatย twoย valuesย ofย resistanceย willย theย powerย takenย byย theย circuitย beย 172.8 watts, if the impressed 60-cycle emf is 120 volts?

A.ย 85.33 & 3.33 ohms

B.ย 53.33 & 30 ohms

C.ย 5.33 & 3.0 ohms

D.ย 83.33 & 5.33 ohms

Answer: **Option B**

Solution:

239.ย Aย seriesย circuitย composedย ofย 0.2ย Hย inductorย andย aย 74ย ฮผFย capacitorย is connectedย to aย 60ย Vย variableย frequencyย source.ย Atย whatย frequencyย will the current be 4 A with lagging power factor?

A.ย 47.767 Hz

B.ย 74.68 Hz

C.ย 60 Hz

D.ย 50 Hz

Answer: **Option A**

Solution:

240.ย Aย 30ย ohmย resistorย isย connectedย inย parallelย withย anย inductorย ofย 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.ย 7.84 and 7.34

B.ย 47.4 and 47.3

C.ย 44.8 and 84.21

D.ย 84.7 and 34.7

Answer: **Option A**

Solution:

241.ย An impedance of 100 ฮฉ resistance and an unknown inductance is connected across the capacitor. The resulting impedance is a pure resistance of 500ย ฮฉ if ฯ = 10^{5} rad/sec. Calculate the values of inductor and capacitor.

A.ย 1 ฮผF & 2 mH

B.ย 5 ฮผF & 1 mH

C.ย 7 ฮผF & 3 mH

D.ย 0.04 ฮผF & 2 mH

Answer: **Option D**

Solution:

242.ย 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.ย 160 V

B.ย 140 V

C.ย 100 V

D.ย 50 V

Answer: **Option C**

Solution:

243.ย The open circuit voltage ofย an alternator is 127 V and its internal impedance is 10โ 10ยฐ ฮฉ. Find the voltage across a load of 30โ -30ยฐ ฮฉ.

A.ย 100โ -9.7ยฐ V

B.ย 97โ -10ยฐ V

C.ย 79โ -10ยฐ V

D.ย 100โ -7.9ยฐ V

Answer: **Option A**

Solution:

244.ย 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.ย 0.707

B.ย 0.83

C.ย 0.85

D.ย 0.965

Answer: **Option D**

Solution:

245.ย 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 isย supplied by 50 V, 50 Hz supply.

A.ย 45 W

B.ย 54 W

C.ย 63 W

D.ย 30 W

Answer: **Option A**

Solution:

246.ย Twoย coilsย Aย andย B are connectedย inย seriesย acrossย a 240ย V,ย 50ย Hzย supply. The resistance of A is 5ย ฮฉย 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.ย 0.0132 H & 8.3 ฮฉ

B.ย 0.215 H & 3.8 ฮฉ

C.ย 0.026 H & 12 ฮฉ

D.ย 0.031 H & 5.3 ฮฉ

Answer: **Option A**

Solution:

247.ย Aย currentย ofย 5ย Aย flowsย throughย aย non-inductiveย resistanceย inย seriesย withย a chokingย coilย whenย suppliedย atย 250ย V,ย 50ย Hz.ย Ifย theย voltageย acrossย the resistanceย isย 120ย Vย andย acrossย theย coilย isย 200ย V,ย calculateย theย power absorbed by the coil in watts.

A.ย 168.75 W

B.ย 137.5 W

C.ย 51.37 W

D.ย 75.31 W

Answer: **Option A**

Solution:

248.ย A single phase, 7.46 kW motor is supplied from a 400 V, 50 Hz AC mains. If itsย efficiencyย isย 85%ย andย theย powerย factorย isย 0.8ย lagging,ย findย theย reactive component of the input current.

A.ย 16.46 A

B.ย 21.95 A

C.ย 27.43 A

D.ย 21 A

Answer: **Option A**

Solution:

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

A.ย 35.18 ฮผF

B.ย 47.9 ฮผF

C.ย 27.8 ฮผF

D.ย 30.7 ฮผF

Answer: **Option C**

Solution:

250.ย A 3 HP, 120 V, 60 Hz induction motor operating at 80% efficiency and 0.866 laggingย powerย factorย isย toย beย usedย temporarilyย withย 240ย V,ย 60ย Hzย source. Whatย resistanceย inย seriesย withย theย motorย willย beย requiredย forย theย motorย to have 120 V across its terminals at full load?

A.ย 6.68 ฮฉ

B.ย 4.77 ฮฉ

C.ย 13.76 ฮฉ

D.ย 9.54 ฮฉ

Answer: **Option B**

Solution:

โ 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:

**MCQ in AC Circuits**

**MCQ from Number 1 โ 50**Answer key:

**included**

**MCQ from Number 51 โ 100**Answer key:

**included**

**MCQ from Number 101 โ 150**Answer key:

**included**

**MCQ from Number 151 โ 200**Answer key:

**included**

**MCQ from Number 201 โ 250**Answer key:

**included**

**MCQ from Number 251 โ 300**Answer key:

**included**

**MCQ from Number 301 โ 350**Answer key:

**included**

**MCQ from Number 351 โ 400**Answer key:

**included**

**MCQ from Number 401 โ 450**Answer key:

**included**

**MCQ from Number 451 โ 500**Answer key:

**included**

**MCQ in AC Circuits Series**

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please include solutions so that we can see our mistakes cause some didnt match with my final answer