MCQ in Power Generators (Cells and Batteries) Part 7 | ECE Board Exam

(Last Updated On: May 3, 2019)

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

Choose the letter of the best answer in each questions.

301. In dc motors, power loss is contributed greatly by

A. flux loss

B. core loss

C. copper loss

D. mechanical friction

302. Dirt on the commutator may produce

A. isolation

B. excessive sparking

C. power loss

D. lower torque

303. Motor vibrations are usually caused by

A. loose coupling

B. dirt on the commutator

C. much brush tension

D. worn bearings

304. When a motor is overloaded, it will usually

A. slow down

B. speed up

C. vibrate

D. overheat

305. Which motor that produces the highest increase in torque considering the same increase in current?

A. dc shunt

B. dc series

C. differentially compounded

D. cumulatively compounded

306. When an armature opens in dc motor, it may cause

A. intermittent sparking

B. an increase in speed

C. the motor to slow down

D. the motor to stop rotating

307. Why do motors take large current during starting?

A. the armature resistance is still low

B. the field produced is still weak

C. it has to break the momentum

D. there’s still a low back emf

308. In dc motors, the speed will

A. increase with an increase in field strength

B. decrease with an increase in field strength

C. decrease as the supply voltage is increased

D. B and C are correct

309. When armature current is increased in a dc motor, its armature reaction will

A. also increase

B. decrease

C. increase exponentially

D. decrease exponentially

310. Why does in dc motor, brushes are positioned such that they will be with the direction of the rotation?

A. to reduce sparking

B. to last long

C. to have less loss

D. all of the above

311. Motors are used to convert electrical energy to mechanical energy. What type of motor that is best suited for heavy-load application?

A. dc series motors

B. dc compound motors

C. single phase motors

D. polyphase motors

312. DC shunt motor speed can be controlled electronically by using a _______ in series with the armature winding.

A. thyrector

B. potentiometer

C. rheostat

D. thyristor

313. Which thyristor is commonly used is motor speed control?

A. triac

B. diac

C. SCR

D. SUS

314. In controlling motor speed, the SCRs controls the

A. number of pulses

B. phase angle

C. firing angle

D. any of these

315. How do you reverse the rotation of a dc shunt motor?

A. By reversing the direction of the field current, leaving the armature current the same.

B. By reversing the direction of the armature current, leaving the field current the same.

C. By reversing both field and armature current

D. Either A or B

316. In motor speed control, what is responsible for SCR firing?

A. trigger circuit

B. threshold circuit

C. reference circuit

D. holding circuit

317. A circuit that converts ac-voltage to dc-voltage

A. rectifier

B. inverter

C. dc-converter

D. ac-converter

318. Conversion from dc-voltage to another dc-voltage requires a

A. inverter

B. cycloconverter

C. dc-converter

D. ac-converter

319. A converter that changes ac-voltage to another ac-voltage level.

A. inverter

B. cycloconverter

C. dc-converter

D. ac-converter

320. What converter must be used if one wished to change dc-voltage into ac-voltage?

A. inverter

B. cycloconverter

C. dc-converter

D. ac-converter

321. A converter that changes ac-voltage frequency from one to another.

A. inverter

B. cycloconverter

C. dc-converter

D. ac-converter

322. In electronic converters, what signal is mostly used to trigger the active device?

A. sine-wave

B. square-wave

C. triangular-wave

D. sawtooth-wave

323. A transformer consist of the following:

A. An inductance and resistance

B. A parallel resonant circuit

C. A capacitor and an inductor

D. Two coils wound on a common core

324. Transformer is considered by many as an efficient device due to the fact that

A. it uses an inductive coupling

B. it is magnetically coupled

C. it is a static device

D. it is electrically coupled

325. With transformer, what is measured when performing open-circuit test?

A. turns ratio

B. copper loss

C. leakage reactance

D. turns impedance

326. Open-circuit test with transformers is always done on what winding?

A. low-voltage

B. high-voltage

C. primary

D. secondary

327. Short-circuit test with transformers is always done on what winding?

A. low-voltage

B. high-voltage

C. primary

D. secondary

328. When the transformer secondary winding is short-circuited, its primary inductance will

A. become zero

B. decrease

C. increase

D. not be affected

329. Cooling system for transformers with ratings less than 5 kVA

A. forced-air cooling

B. oil-cooling

C. natural air cooling

D. water cooling

330. For transformers, zero efficiency happens when it has

A. no-load

B. 1/2 of full-load

C. 2/3 of full-load

D. full-load

331. For transformers, maximum efficiency happens when

A. copper loss is zero

B. copper loss is equal to constant loss

C. the primary and secondary windings are equal

D. the leakage reactances of both windings are equal

332. In constructing transformers, the primary and secondary windings should have

A. good electrical coupling

B. loose magnetic coupling

C. tight magnetic coupling

D. best inductive coupling

333. What are the two parameters in transformers that are the same in both primary and secondary?

A. power and voltage

B. power and current

C. power and impedance

D. voltage per turn and ampere-turns

334. In transformers, the amount of copper used in the primary is

A. less than that of the secondary

B. greater than that of secondary

C. exactly twice that of secondary

D. almost equal as that of secondary

335. At very low frequencies, transformers woks poorly because

A. its magnetizing current will be very high

B. its core permeability will be greatly increased

C. its core permeability will be greatly reduced

D. its impedance will increase

336. What will happen if a power transformer is to be operated at a very high frequency?

A. it will have a very high core loss

B. its impedance will decrease

C. its core permeability will be greatly increased

D. its core permeability will be greatly reduced

337. How are the primary and secondary coupled in autotransformers?

A. electrically

B. magnetically

C. electrically and magnetically

D. capacitively

338. In a single-phase transformer, the core flux is

A. constant

B. pulsating

C. alternating

D. alternating and sometimes stable

339. What do you think will happen to a transformer when its primary is connected to a DC supply?

A. It will become more efficient

B. It will become less efficient

C. It will have good regulation

D. It might burn out

340. Generally, in what application you consider the use of core-type transformers?

A. low voltage and low current

B. low voltage and high current

C. high voltage and low current

D. high voltage and high current

341. In ________ transformers, when its primary is energized the secondary should never be open-circuited.

A. power

B. voltage

C. current

D. matching

342. Considered as an ideal transformer

A. the one with no losses and leakage reactance

B. the one with 100% regulation

C. the one with zero efficiency

D. the one with equal primary and secondary

343. What is the effect of air gaps at the transformer core?

A. Its reluctance is decreased

B. It increases eddy current

C. It decreases hysteresis loss

D. It increases magnetizing current

344. ________ currents are wasteful currents which flows in cores of transformers and produces heat.

A. Residual

B. Eddy

C. Sneak

D. Magnetizing

345. What will happen to the eddy current loss in transformers when the load is increased?

A. will also increase

B. will decrease

C. will become infinite

D. nothing will happen

346. Leakage flux in transformers will cause

A. copper loss to increase

B. copper loss to decrease

C. eddy current to decrease

D. voltage drop in the windings

347. The increase in temperature in a transformer is mainly due to

A. true power

B. reactive power

C. apparent power

D. virtual power

348. In transformers, the voltage per turn at the primary is ________ the secondary.

A. less than that of

B. greater than that of

C. a factor of

D. the same as

349. In transformer windings, the more number of turns

A. the higher is the voltage

B. the lower is the voltage

C. the lower is the impedance

D. the higher is the current

350. What is true about core-type transformers?

A. It has a shorter magnetic path

B. It has a longer magnetic path

C. It has a very long magnetic path

D. It has an infinite magnetic path

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

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

Complete List of MCQ in Electronics Engineering per topic