This is the Multiple Choice Questions Part 6 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 6 of the Series

SERIES CIRCUITS

**Choose the letter of the best answer in each question.**

โ MCQ in AC Circuits Part 5 | REE Board Exam

251.ย A circuit draws a current of (3 โ j8) A from a source of (100 + j37) V. Find the true power of the circuit.

A.ย 4 W

B.ย 596 W

C.ย 300 W

D.ย 296 W

252.ย A resistor andย aย coil are connectedย inย series with aย voltage source.ย If the voltage acrossย theย coilย isย 10 sinย (866t + 70ยฐ) V and the currentย flowing through the resistor is 2 cos (866t โ 80ยฐ) A, what is the resistance of the coil?

A.ย 4.92 ฮฉ

B.ย 2.5 ฮฉ

C.ย 5 ฮฉ

D.ย 4.33 ฮฉ

Answer: **Option B**

Solution:

253.ย A coil has a resistance of 6 ohms and an inductance of 0.02 H. When a noninductive resistor is connected in series with the coil, the current drawn when connected to 220 V DC source is equal to the current drawn by the coil alone across a 220 V, 60 Hz source. Determine the resistance of the non-inductive resistor.

A.ย 3.63 ฮฉ

B.ย 6.39 ฮฉ

C.ย 3.69 ฮฉ

D.ย 3.96 ฮฉ

254.ย A series RL circuit has L = 0.02 H and an impedance of 17.85ย ฮฉ. When a sinusoidal voltage is applied, the current lags the voltage by 63.5ยฐ. What is the value of the angular frequency?

A.ย 400 rad/sec

B.ย 500 rad/sec

C.ย 600 rad/sec

D.ย 800 rad/sec

255.ย A 50 ฮฉ resistance is connected in series with a coil having 25 ฮฉ resistance and 150 mH inductance. The circuit is connected to a voltage source of 200 sin ฯt. Calculate the instantaneous current.

A.ย 2.9 sin ฯt

B.ย 1.7 sin (ฯt + 37ยฐ)

C.ย 2.1 sin (ฯt โ 37ยฐ)

D.ย 5.11 sin (ฯt – 37ยฐ)

256. A coil having a resistance of 25 ฮฉ and an inductance of 150 mH is connected inย series with anย 80ย ฮผF capacitor acrossย aย voltage source of 200 sinย 377t. What is its instantaneous current?

A.ย 5.84 cos (377t – 43ยฐ)

B.ย 5.84 sin 377t

C.ย 5.84 sin (377t + 43ยฐ)

D.ย 5.84 sin (377t – 43ยฐ)

257.ย A coil with a 15 ฮฉ resistance is connected in series with a capacitor. At 60 Hz source, the impedance is measured at 15 + j11.27 ฮฉ while in 30 Hz source it is measured as 15 โ j7.24 ฮฉ. Calculate the inductance of the coil.

A.ย 52.7 mH

B.ย 65.8 mH

C.ย 41.2 mH

D.ย 11.27 mH

258.ย An impedance coil has a resistance and inductance of 20 ohms and 0.05 H respectively. What value of dc voltage can be applied to the coil in order that it will take the same power from a 220 V 60 Hz mains?

A.ย 188 V

B.ย 220 V

C.ย 160 V

D.ย 120 V

259.ย Aย ยฝย HP,ย 110ย V,ย 60ย Hz,ย single-phaseย inductionย motorย hasย anย efficiencyย of 88%ย and a power factor of 0.707 lagging at rated load. This motor is to be connectedย temporarilyย onย aย 220ย V,ย 60ย Hzย line.ย Determineย theย resistance required to be placed in series with the motor in order to prevent the machine from experiencing overcurrent?

A.ย 25.2 ohms

B.ย 23.5 ohms

C.ย 19.5 ohms

D.ย 27.6 ohms

Answer: **Option B**

Solution:

260.ย Two coils Aย and B known to haveย theย same resistance are connected in series across a 110 V, 60 cycle line. The current and power delivered by the source are respectively 4.1 A and 300 W. If the voltage across coil A is twice that across coil B, calculate the inductance of coil B.

A.ย 8.63 mH

B.ย 7.36 mH

C.ย 9.02 mH

D.ย 4.49 mH

261.ย The total voltage in a series RL circuit ____ the current by an angle ____.

A.ย lags, of 90ยฐ

B.ย lags, between 0ยฐ and 90ยฐ

C.ย leads, between 0ยฐ and 90ยฐ

D.ย leads, between 90ยฐ and 180ยฐ

Answer: **Option C**

Solution:

262.ย In a series RL circuit, the inductor current ____ the resistor current.

A.ย lags

B.ย is equal

C.ย leads

D.ย is negative

Answer: **Option A**

Solution:

263.ย Theย impedanceย triangleย isย similarย toย theย ____ย triangleย withย theย resistance phasor in place of the ____.

A.ย current, resistor current

B.ย current, resistor voltage

C.ย voltage, impedance

D.ย voltage, resistor voltage

Answer: **Option C**

Solution:

264.ย In the impedance triangle the inductive reactance and impedance phasor are analogous to the ____ and ____ phasor respectively in the voltage triangle.

A.ย inductive voltage, total voltage

B.ย inductive current, total current

C.ย inductive voltage, resistive current

D.ย inductive current, resistive current

Answer: **Option A**

Solution:

265.ย In a series RL circuit, phasor diagram, total voltage may be represented by theย ____ย phasor andย theย resistor voltageย may beย representedย byย theย ____ voltage.

A.ย current, voltage

B.ย impedance, resistance

C.ย current, resistance

D.ย impedance, inductance

Answer: **Option B**

Solution:

266.ย The phase angle of a series RL circuit is the angle between the ____ phasor and the ____ phasor.

A.ย resistance, inductive reactance

B.ย resistance, impedance

C.ย inductive reactance, impedance

D.ย none of the above

Answer: **Option B**

Solution:

267.ย Theย phase angle of a series RL circuit may be computed ____ as ____ or ____.

A.ย cos^{-1} R/X_{L}, sin^{-1} X_{L}/R, tan^{-1} R/Z

B.ย cos^{-1} R/Z, sin^{-1} X_{L/}R, tan^{-1} R/XL

C.ย cos^{-1} Z/X_{L}, sin^{-1} R/Z, tan^{-1} X_{L}/R

D.ย cos^{-1} R/Z, sin^{-1} X_{L}/Z, tan^{-1} X_{L}/R

Answer: **Option D**

Solution:

268.ย In the circuit of figure shown the effective value of the resistor voltage isย ____ volts.

A.ย 5 โ2

B.ย 5

C.ย 5/โ2

D.ย 10

Answer: **Option A**

Solution:

269.ย A(n) ____ stores and returns energy to a circuit while a(n) ____ dissipates energy.

A.ย resistor, impedance

B.ย resistor, inductor

C.ย inductor, resistor

D.ย inductor, reactance

Answer: **Option C**

Solution:

270.ย For an RL circuit, the power factor cannot be less than ____ or greater than ____.

A.ย 0, 1

B.ย 1, 0

C.ย 0, -1

D.ย โ1, 0

Answer: **Option A**

Solution:

271.ย The voltage across a capacitor ____ the current through it by ____.

A.ย lags, 45ยฐ

B.ย lags, 90ยฐ

C.ย leads, 0ยฐ

D.ย leads, 90ยฐ

Answer: **Option B**

Solution:

272.ย If the resistanceย inย aย series RC circuit is increasedย the magnitudeย ofย thephase angle

A.ย increases

B.ย remains the same

C.ย decreases

D.ย changes to an indeterminate manner

Answer: **Option C**

Solution:

273.ย In a series RC circuit, the current ____ the total voltage by an angle.

A.ย lags, of 45ยฐ

B.ย lags of 0ยฐ

C.ย leads, between 0ยฐ and 90ยฐ

D.ย leads, of 90ยฐ

Answer: **Option C**

Solution:

274.ย Theย resistanceย phasorย forย aย seriesย RCย circuitย pointsย toย theย right.ย The capacitive reactance phasor points ____ while theย diagonal of the rectangle having there two phasors as sides represents the ____.

A.ย up, impedance

B.ย left, current

C.ย down, impedance

D.ย up, total voltage

Answer: **Option C**

Solution:

275.ย The phase angle for a series RC circuit is defined as the angle between the ____ and the ____ phasors.

A.ย current, resistance voltage

B.ย current, total voltage

C.ย resistance voltage, capacitor voltage

D.ย R, X_{C}

Answer: **Option B**

Solution:

276.ย The phaseย angleย for aย series RC circuit may beย computed asย the angle between the ____ and the ____ phasors.

A.ย resistance, impedance

B.ย resistance, reactance

C.ย resistance, impedance

D.ย none of these

Answer: **Option A**

Solution:

277.ย If a series RC circuit with 10 ohms and X_{C} = 10 ohms carries a current of 1 ampereย effectiveย valueย theย resistorย voltageย isย ____ย voltsย effectiveย andย the capacitor voltage is ____ volts effective.

A.ย 10/โ2 , 10/โ2

B.ย 10, 10

C.ย 10โ2 , 10โ2

D.ย 5, 10

Answer: **Option B**

Solution:

278.ย Theย powerย dissipated inย a series RL circuitย withย R =10ย ohmsย andย X_{C} = 10 ohms carrying an effective current of 3 amps is _____ watts.

A.ย 30

B.ย 30โ2

C.ย 90

D.ย 90โ2

Answer: **Option C**

Solution:

279.ย The magnitude of the power factor ofย an RC circuit with R = 10 ohms, X_{C}ย = 10 ohms. I = 2 amp effective is ______.

A.ย 1

B.ย 0.5

C.ย 0.707

D.ย 0.02

Answer: **Option C**

Solution:

280.ย The power dissipated in the circuit shown is ____ watts.

A.ย 60

B.ย 80

C.ย 100

D.ย 120

Answer: **Option D**

Solution:

281.ย The net reactance in an RLC circuit is

A.ย X_{Lย }

B.ย X_{C} โ X_{Lย }

C.ย X_{C}

D.ย X_{L} – X_{C}

Answer: **Option D**

Solution:

282.ย The impedance of a series RLC circuit is ______.

A.ย โ(R^{2} + X_{L}^{2} + X_{C}^{2})

B.ย โ(R^{2} + X_{L}^{2} – X_{C}^{2})

C.ย โ(R^{2} + (X_{L}ย + X_{C})^{2})

D.ย โ(R^{2} + (X_{L}ย – X_{C})2)

Answer: **Option D**

Solution:

283.ย In a series RC circuit, the voltage across the capacitor and the resistor are 60 V and 80 V respectively. The input voltage should be

A.ย 70โ 45ยฐ V

B.ย 100โ -37ยฐ V

C.ย 105โ -42ยฐ V

D.ย 108โ -60ยฐ V

Answer: **Option B**

Solution:

284.ย The transient current are due to

A.ย voltage applied to circuit

B.ย resistance of the circuit

C.ย impedance of the circuit

D.ย changes in stored energy in inductance and capacitance

Answer: **Option D**

Solution:

285.ย To aย highly inductive circuit, a small capacitance isย addedย in series.ย The angle between voltage and current will

A.ย increase

B.ย decrease

C.ย remain nearly the same

D.ย become indeterminant

Answer: **Option B**

Solution:

286.ย In a series R-L circuit. V_{L} ____ V_{R} by ____ degrees.

A.ย lags, 45

B.ย lags, 90

C.ย leads, 90

D.ย leads, 45

Answer: **Option C**

Solution:

287.ย The voltage applied across an R-L circuit is equal to _____ of V_{R} and V_{L}.

A.ย arithmetic sum

B.ย algebraic sum

C.ย phasor sum

D.ย sum of the squares

Answer: **Option C**

Solution:

288.ย The power in an a.c. circuit is given by

A.ย VI cos ฯ

B.ย VI sin ฯ

C.ย Iยฒ Z

D.ย Iยฒ X_{L}

Answer: **Option A**

Solution:

289.ย The p.f. of an R-C circuit is

A.ย often zero

B.ย between zero and 1

C.ย always unity

D.ย between zero and -1.0

Answer: **Option B**

Solution:

290.ย Which phasor diagram is correct for a series R-C circuit?

A.ย Figure 1

B.ย Figure 2

C.ย Figure 3

D.ย Figure 4

Answer: **Option B**

Solution:

291.ย In an R-L-C circuit, v(t) = 20 sin (314t + 5ฯ/6) and i(t) = 10 sin (314t + 2ฯ/3). The p.f. of the circuit is ____ and power drawn is ____ watt.

A.ย 0.5 lead, 200

B.ย 0.886 lag, 186.6

C.ย 0.866 lead, 173.2

D.ย 0.5 lag, 50

Answer: **Option B**

Solution:

292.ย The input of an a.c. circuit having p.f. of 0.8 lagging is 20 kVA. The power drawn by the circuit is ____ kW.

A.ย 12

B.ย 20

C.ย 16

D.ย 8

293.ย The power factor of an a.c. circuit is given by

A.ย cosine of the phase angle

B.ย tangent of the phase angle

C.ย the ratio R/X_{L}

D.ย the ratio X_{L}/Z

Answer: **Option A**

Solution:

294.ย In series R-L-C circuit, R = 100 โฆ, X_{L}ย = 300 โฆ and X_{C}ย = 200 โฆ. The phase angle ฮฆ of the circuit is _____ degrees.

A.ย 0

B.ย 90

C.ย 45

D.ย -45

Answer: **Option C**

Solution:

295.ย The phase angle of a series R-L-C circuit is leading if

A.ย X_{L} = 0

B.ย R = 0

C.ย X_{C} > X_{L}

D.ย X_{C} < X_{L}

Answer: **Option C**

Solution:

296.ย In an a.c. circuit, the ratio of kW/kVA represents

A.ย power factor

B.ย load factor

C.ย form factor

D.ย diversity factor

Answer: **Option A**

Solution:

297.ย If p.f. of a circuit is unity, its reactive power is

A.ย a maximum

B.ย equal to IยฒR

C.ย zero

D.ย a negative quantity

Answer: **Option C**

Solution:

298.ย An R-L-C circuit has R = 10 โฆ, X_{L} = 20 โฆ and X_{C} = 30 โฆ. The impedance of the circuit is given by the expression.

A.ย Z = 10 + j20

B.ย Z = 10 + j50

C.ย Z = 10 โ j20

D.ย Z = -10 + j20

Answer: **Option C**

Solution:

299.ย An alternating voltage e = 200 sin 314t is applied to a device which offers an ohmic resistance of 20 ฮฉ to the flow of current in one direction while entirely preventingย theย flow inย theย oppositeย direction. Theย average value of current will be

A.ย 5 A

B.ย 3.18 A

C.ย 1.57 A

D.ย 1.10 A

Answer: **Option B**

Solution:

300.ย A 10 mH inductor carries a sinusoidal current of 1 A rms at a frequency of 50 Hz. The average power dissipated by the inductor is

A.ย 0 W

B.ย 0.25 W

C.ย 0.5 W

D.ย 1.0 W

Answer: **Option A**

Solution:

โ MCQ in AC Circuits Part 7 | 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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