Industrial Electronics: Principles and Applications - MCQs Part V

Compiled MCQs in Industrial Electronics: Principles and Applications part 5. Topic includes Electronic Control System, Solid State Services, welding, thyristors, transducers, control systems, robotics, instrumentation control.

MCQs in  Industrial Electronics: Principles and Applications - MCQs Part V

This is the Multiples Choice Questions Part 5 of the Series in Industrial Electronics: 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.

Multiple Choice Questions Topic Outline

  • MCQs in Industrial Electronics
  • MCQs in Electronic Control System
  • MCQs in Industrial Solid State Services
  • MCQs in Welding Systems
  • MCQs in Thyristors
  • MCQs in High Frequency Heating
  • MCQs in Feedback Systems / Servomechanism
  • MCQs in Transducers
  • MCQs in Motor Speed Control Systems
  • MCQs in Robotic Principles
  • MCQs in Bioelectrical Principles
  • MCQs in Instrumentation and Control

The Series

Following is the list of multiple choice questions in this brand new series:

Industrial Electronics Principles and Applications MCQs
PART 1: MCQs from Number 1 – 50                        Answer key: PART I
PART 2: MCQs from Number 51 – 100                   Answer key: PART II
PART 3: MCQs from Number 101 – 150                 Answer key: PART III
PART 4: MCQs from Number 151 – 200                 Answer key: PART IV
PART 5: MCQs from Number 201 – 250                 Answer key: PART V
PART 6: MCQs from Number 251 – 300                 Answer key: PART VI

Continue Part V of the MCQs Series

201. For an SCR, dv/dt protection is achieved through the use of:</>

  • A.  RL in series with SCR
  • B.   RC across SCR
  • C.  L in series with SCR
  • D. RC in series with SCR

202. A technique use to turn off a thyristor using an external circuit which causes the anode to become negatively biased.

  • A. force commutation
  • B. reverse triggering
  • C. negative feedback
  • D. doping

203. The turn-off time of thyristor is 30 m sec at 50°C. Its turn-off time at 100° is

  • A. same
  • B. 15 m sec
  • C. 60 m sec
  • D. 100 m sec

204. The peak and valley currents of the PUT are typically _____ those of a similarly rated UJT.

  • A. lower than
  • B. the same as
  • C. higher than
  • D. None of the above

205. What is a solid state equivalent of a gas filled triode?

  • A. Triac
  • B. Thyristor
  • C. SCR
  • D. SCS

206. The method(s) for turning off an SCR is (are) categorized as _____.

  • A. current interruption
  • B. forced commutation
  • C. both current interruption and forced commutation
  • D. None of the above

207. In a certain UJT rB1 is 2.5 kΩ and rB2 = 4 kΩ. What is the intrinsic standoff ratio?

  • A. 0.61538
  • B. 0.38461
  • C. 2.6
  • D. 0.8125

208. When SCR starts conducting, then _____ losses all control.

  • A. gate
  • B. anode
  • C. cathode
  • D. anode supply

209. You have the schematic diagram of several types of circuits. Which of these circuits most likely uses a triac?

  • A. an oscillator
  • B. an ac motor control
  • C. a programmable oscillator
  • D. an amplifier

210. Determine RB1 for a silicon PUT if it is determined that h = 0.84, VP = 11.2 V, and RB2 = 5 kΩ.

  • A. 12.65 kΩ
  • B. 16.25 kΩ
  • C. 20.00 kΩ
  • D. 26.25 kΩ

211. Which of the following devices does not have a cathode terminal?

  • A. SCR
  • B. SCS
  • C. TRIAC
  • D. Shockley diode

212. The UJT operates in what region after peak point?

  • A. Cut off
  • B. Negative resistance
  • C. Saturation
  • D. Positive resistance

213. What is basically a two-terminal parallel-inverse combination of semiconductor layers that permits triggering in either direction?

  • A. DIAC
  • B. TRIAC
  • D. Shockley Diode

214. Which device does not have a gate terminal?

  • A. Triac
  • B. SCR
  • C. FET
  • D. Diac

215. The four-layer devices with a control mechanism are commonly referred to as _____.

  • A. thyristors
  • B. transistors
  • C. diodes
  • D. None of the above

216. What is that voltage above when the SCR enters the conduction region?

  • A. Reverse breakover voltage
  • B. Forward breakover voltage
  • C. Holding voltage
  • D. Trigger voltage

217. It is a three-terminal silicon diode with the ability to control a large ac power with a small signal.

  • A. TRIAC
  • B. SCR
  • C. UJT
  • D. SCS

218. The smallest amount of current that the cathode-anode can have, and still sustain conduction of an SCR is called the:

  • A. maximum forward current
  • B. maximum forward gate current
  • C. holding current
  • D. reverse gate leakage current

219. It is the minimum additional current that can make up for any missing input (gate) current in order to keep the device ON.

  • A. leakage current
  • B. ac current
  • C. holding current
  • D. switching current

220. The PUT (programmable unijunction transistor) is actually a type of:

  • A. UJT thyristor
  • B. FET device
  • C. TRIAC
  • D. SCR

221. What is the typical value of the interbase resistance of UJTs?

  • A. 20 KΩ
  • B. Between 4 to 4 KΩ
  • C. 4 KΩ
  • D. Between 4 to 10 KΩ

222. Which of the following is a four-layer diode with an anode gate and a cathode gate?

  • A. SCS
  • B. SCR
  • C. SBS
  • D. SUS

223. SCR is a rectifier constructed of silicon material. Silicon is chosen because

  • A. it is the most abundant material
  • B. of its strength and ruggedness
  • C. it is much cheaper than any other material
  • D. of its high temperature and power capabilities

224. When the temperature increases, the intrinsic standoff ratio

  • A. increases
  • B. decreases
  • C. essentially constant
  • D. becomes zero

225. SCRs have been designed to control powers as high as _____, with individual ratings as high as _____ at _____.

  • A. 1800 MW, 10 A, 2000 V
  • B. 1800 MW, 2000 A, 10 V
  • C. 10 MW, 2000 A, 1800 V
  • D. 2000 MW, 10 A, 1800 V

226. An SCR is a member of what family?

  • A. Thyrector
  • B. Thyratron
  • C. Thyristor
  • D. Transistor

227. Which of the following can change the angle of conduction in SCR?

  • A. Changing anode voltage
  • B. Changing gate voltage
  • C. Reverse biasing the gate
  • D. Changing cathode voltage

228. What is the frequency range of application of SCRs?

  • A. About 10 kHz
  • B. About 50 kHz
  • C. About 250 kHz
  • D. About 1 mHz

229. The minimum operating voltage of the UJT is typically _____ that of a similarly rated PUT.

  • A. lower than
  • B. the same as
  • C. higher than
  • D. None of the above

230. A UJT is sometimes called a ____ diode.

  • A. double-based
  • B. single-based
  • C. a rectifier
  • D. a switching diode

231. It is like a low current SCR with two gate terminals.

  • A. UJT
  • B. PUT
  • C. SCR
  • D. SCS

232. What is the typical value of the reverse resistance of SCRs?

  • A. 1 Ω to 10 Ω
  • B. 100 Ω to 1 kΩ
  • C. 1 kΩ to 50 kΩ
  • D. 100 kΩ or more

233. Which of the following is the normal way to turn on a diac?

  • A. By breakover voltage
  • B. By gate voltage
  • C. By gate current
  • D. By anode current

234. In a SCR circuit, the angle of conduction can be changed by changing

  • A. anode voltage
  • B. anode current
  • C. forward current rating
  • D. gate current

235. The function of snubber circuit connected across the SCR is to:

  • A. Suppress dv/dt
  • B. Increase dv/dt
  • C. Decrease dv/dt
  • D. Decrease di/dt

236. An SCR is made of what material?

  • A. Silicon
  • B. Carbon
  • C. Germanium
  • D. Gallium-arsenide

237. The SCR can exercise control over _____ of ac supply.

  • A. positive or negative half-cycle
  • B. both positive and negative half-cycles
  • C. only positive half-cycle
  • D. only negative half-cycle

238. Which of the following conditions is necessary for triggering system for thyristors?

  • A. It should be synchronized with the main supply
  • B. It must use separate power supply
  • C. It should provide a train of pulses
  • D. None of these

239. A normally operated SCR has an anode which is _____ with respect to cathode.

  • A. negative
  • B. positive
  • C. at zero potential
  • D. at infinite potential

240. Which of the following devices has (have) four layers of semiconductor materials?

  • A. Silicon-controlled switch (SCS)
  • B. Gate turn-off switch (GTO)
  • C. Light-activated silicon-controlled rectifier (LASCR)
  • D. All of the above

241. How many pn junction does SCRs have?

  • A. Two
  • B. Four
  • C. Three
  • D. Five

242. The silicon-controlled switch (SCS) is similar in construction to the

  • A. triac.
  • B. diac.
  • C. SCR.
  • D. 4-layer diode.

243. Which of the following devices has nearly the same turn-on time as turn-off time?

  • A. SCR
  • B. GTO
  • C. SCS
  • D. LASCR

244. Which of the following is (are) the advantages of the SCS over a corresponding SCR?

  • A. Reduced turn-off time
  • B. Increased control and triggering sensitivity
  • C. More predictable firing situation
  • D. All of the above

245. An effect that reduces the possibility of accidental triggering of the SCS.

  • A. Miller effect
  • B. Rate effect
  • C. End effect
  • D. Flywheel effect

246. An SCR whose state is controlled by the light falling upon a silicon semiconductor layer of the device.

  • A. SCS
  • B. GTO
  • C. Thyristor
  • D. LASCR

247. Power electronics deals with the control of ac power at what frequencies essentially?

  • A. 20 KHz
  • B. 1000 KHz
  • C. Frequencies less than 10 Hz
  • D. 60 Hz frequency

248. To turn on the UJT, the forward bias on emitter diode should be _____ the peak point voltage.

  • A. more than
  • B. less than
  • C. equal to
  • D. twice

249. What is the resistance of a certain 4-layer diode in the forward-blocking region if VAK = 15V and IA = 1 uA

  • A. 15 Ω
  • B. 21.21 MΩ
  • C. 15 M Ω
  • D. 10.61 MΩ

250. What is the peak-point voltage for the UJT in problem 76 if VBB = 15V?

  • A. 10.605
  • B. 5.76912
  • C. 6.46915
  • D. 0.8125

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