MCQ in Power Generators (Cells and Batteries) Part 8 | ECE Board Exam

This is the Multiples Choice Questions Part 8 of the Series in Power Generators, Sources, Principles and Applications as one of the Electronics Engineering topic. In Preparation for the ECE 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 Electronics Engineering field, Electronics Books, Journals and other Electronics References.

MCQ Topic Outline included in ECE Board Exam Syllabi

• MCQ in Cells and Batteries
• MCQ in Electric Generator
• MCQ in Electronic Power Supply
• MCQ in Voltage Regulation
• MCQ in Photovoltaic/Thermoelectric Generator
• MCQ in Distribution Transformer
• MCQ in Uninterrupted Power Supply (UPS)
• MCQ in Float-Battery System
• MCQ in Converters
• MCQ in Inverters

Continue Practice Exam Test Questions Part 8 of the Series

Choose the letter of the best answer in each questions.

351. Practically how many percent is copper loss to the total loss in transformers?

A. 15%

B. 50%

C. 85%

D. 100%

352. What is the purpose of laminating the core of a transformer?

A. to decrease eddy current loss

B. to increase eddy current loss

C. to decrease copper loss

D. to decrease hysteresis loss

353. Large transformers have approximately an efficiency of

A. 25%

B. 45%

C. 75%

D. 95%

354. The loss in a transformer due to the changing field is called

A. leakage

B. hysteresis loss

C. eddy loss

D. keeper

355. The ratio of the amount of magnetic flux linking a secondary coil compared to the flux generated by the primary coil:

A. coupling factor

B. mutual coupling

C. coefficient of coupling

D. hysteresis factor

356. Mutual inductance between two coils can be decreased by

A. moving the coils apart

B. inserting an iron core

C. moving the coils close

D. reducing the reluctance

357. An advantage of full-wave rectifier over half-wave rectifier.

A. Each diode can cool-off during half of each input cycle

B. The ripple frequency is lower

C. The tube will conduct during both halves of the input cycle

D. Output voltage is lower with more ripple

358. One of the following items below is not one of the main components of an alternating current power supply.

A. Power transformer

B. Voltage regulator

C. Rectifier

D. Filter

359. Most electronic devices/circuits require dc-voltage to operate. A battery is a good power source, however, its operating time is limited. The use of battery also proves to be expensive. A more practical alternative is to use the household main supply, and since this is an ac-voltage, it must be converted to a dc-voltage. The circuit that converts this ac-voltage to a dc-voltage is called

A. rectifier

B. clamper

C. filter

D. regulator

360. A rectifier that uses either the positive or negative portion only of the main ac-supply

A. half-wave

B. full-wave

C. full-wave bridge

D. all of the above

361. For a half-wave rectifier, the average output voltage is _______ of the maximum ac voltage.

A. 31.8%

B. 45%

C. 63.6%

D. 90%

362. Percent ripple of a half-wave rectifier.

A. 24%

B. 48%

C. 63.6%

D. 121%

363. Calculate the dc-voltage at the output of a half-wave rectifier with a 12Vrms input.

A. 2.7 V

B. 3.8 V

C. 4.5 V

D. 5.4 V

364. To double the capability of the half-wave rectifier, a __________ must be used.

A. full-wave rectifier

B. full-wave bridge

C. dual-supply

D. A or B is correct

365. Full-wave rectifier defers from full-wave bridge in what aspect?

A. full-wave uses two diodes, while four for full-wave bridge

B. diode’s PIV in full-wave is twice that of full-wave bridge

C. full-wave generates less heat than full-wave bridge

D. all of the above

366. Common to both full-wave and full-wave bridge rectifiers

A. dc-voltage

B. ripple factor

C. ripple frequency and percent ripple

D. all are correct

367. Find direct current voltage from a full-wave rectifier with 120 V peak rectified voltage.

A. 60 V

B. 7.639 V

C. 76.39 V

D. 6.0 V

368. The dc-voltage of a full-wave bridge rectifier.

A. 0.318 Vmax

B. 0.45 Vmax

C. 0.636 Vmax

D. 0.90 Vmax

369. Relate the magnitude of the dc-output voltage to the ac input rms voltage of a full-wave rectifier.

A. VDC = 0.318 Vrms

B. VDC = 0.45 Vrms

C. VDC = 0.636 Vrms

D. VDC = 0.90 Vrms

370. Determine the dc-voltage of a full-wave bridge rectifier when the input ac-voltage is 24 Vrms.

A. 7.63 V

B. 10.8 V

C. 15.3 V

D. 21.6 V

371. Ripple factor of a full-wave rectifier.

A. 0.318

B. 0.48

C. 0.9

D. 1.21

372. To improve the dc output voltage of a power supply, a __________.

A. shunt resistor may be installed

B. limiting resistor may be installed

C. feedback element may be installed

D. filter capacitor may be installed

373. Factor(s) that can reduce the ripple voltage of a power supply.

A. filter capacitance

B. reduction of load current

C. increase in input frequency

D. all of the above

374. Making the filter capacitor large in a power supply results to

A. an increase of the ripple voltage

B. an increase of the dc-voltage

C. a decrease of the ripple frequency

D. A and B above

375. Find the ripple factor (kr) of a sinusoidal signal with peak ripple of 4 volts on an average of 30.

A. 0.094

B. 0.013

C. 0.130

D. 0.94

376. Calculate the peak-to-peak ripple voltage of a 20 V full-wave power supply with a filter capacitor C = 220 µF when delivering a load current of 50 mA.

A. 2.0 Vpp

B. 3.79 Vpp

C. 5.67 Vpp

D. 7.9 Vpp

377. In capacitor-filtered power supply, what will happen to the ripple voltage if the load is disconnected?

A. increases

B. becomes infinite

C. becomes unpredictable

D. drops to zero

378. For a power supply with a peak-to-peak ripple voltage of 5 Vpp, determine its rms ripple.

A. 1.44 Vrms

B. 1.77 Vrms

C. 2.88 Vrms

D. 3.54 Vrms

379. A 20-Vdc power supply was found to have a ripple voltage of 2 Vrms when supplying 1.5 amps load. Calculate its percent ripple.

A. 7.5 %

B. 10.0 %

C. 12.5 %

D. 15.0 %

380. Which power supply filter gives the smallest ripple voltage?

A. capacitor filter

B. RC-filter

C. LC-filter

D. multi-section LC-filter

381. Ripple voltage in power supplies causes unwanted effects on the load it is supplying, i.e. a hum in audio amplifiers. To minimize this effect several filtering techniques are used, however, ripple still exists. What is a better alternative to reduce further the ripples?

A. truncation

B. clipping

C. clamping

D. regulation

382. A voltage regulator connected in parallel with the load.

A. series regulator

B. parallel regulator

C. shunt regulator

D. switching regulator

383. Which regulator is the most efficient?

A. series

B. shunt

C. switching

D. modulating

384. Voltage reference element in most voltage regulators

A. diac

B. thyrector

C. zener diode

D. transistor

385. In voltage regulators, what do you call the element/device that controls the amount of current/voltage/power?

A. sampling circuit

B. comparator

C. limiter

D. control element

386. The element/device used as a comparator in most voltage regulators.

A. zener diode

B. BJT

C. IGBT

D. op-amp

387. Sampling circuit used in most voltage regulators.

A. voltage divider network

B. bleeder network

C. crowbar

D. bootstrap circuit

388. Most voltage regulators used __________ as their control element.

A. BJT

B. SBS

C. UJT

D. JFET

389. The most efficient voltage regulator and is therefore used in high-current high-voltage applications.

A. series regulators

B. shunt regulators

C. hybrid regulators

D. switching regulators

390. A 12 VDC power supply is regulated using 7805 IC and is used in TTL circuits that require a 0.2 amps current. Determine the dropout voltage of the system.

A. 4 V

B. 5 V

C. 6 V

D. 7 V

391. A load draws 1 A current from a 10-V regulated power supply. Calculate the power dissipated by the regulator if it has an input voltage of 16 V.

A. 6 Watts

B. 10 Watts

C. 12 Watts

D. 16 Watts

392. Three-terminal fixed positive voltage regulators commonly used in industry.

A. 78XX series

B. 79XX series

C. 723 IC regulator

D. 317 regulator

393. What is the regulated output voltage of a 7924 regulator?

A. + 4 V

B. – 4 V

C. + 24 V

D. – 24 V

394. A three-terminal variable positive voltage regulator

A. 317

B. 337

C. 723

D. 741

395. What three-terminal IC regulator that has a variable negative voltage output?

A. 317

B. 337

C. 723

D. 741

396. In a three-terminal adjustable positive voltage regulator (317), what is the band-gap voltage between the output terminal and adjustment terminal?

A. 1.25 V

B. 2.5 V

C. 3.25 V

D. 4.125 V

397. Typical ripple rejection of most three-terminal voltage regulators

A. 0.1 %

B. 0.8 %

C. 1.2 %

D. 2.0 %

398. The three-terminal voltage regulators, such as the 78XX series has a typical current rating of 1.5 amperes. If a high current is required, say 30 amperes, how will you make modifications from this regulator in order to provide the required current?

A. by cascading them

B. by the use of a crowbar circuit

C. by connecting them in parallel

D. by the use of external pass transistor

399. What is the simplest way of protecting power supplies from reverse-polarity/reverse-current flow?

A. by a forward-biased diode

B. by a reverse-biased diode

C. by a crowbar circuit

D. by a snubber circuit

400. A crowbar circuit is used

A. to monitor the output current of a power supply and automatically shuts down the system when an overload occur.

B. to monitor the temperature of a power supply and switches the cooling fan when a threshold temperature is reached.

C. as voltage reference in regulated power supplies.

D. as an over-voltage protection in power supplies.

Questions and Answers in Power Generators, Sources, Principles, Applications

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