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Wednesday, December 18, 2013

Electricity and Magnetism Fundamentals - MCQs Part V

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Electricity and Magnetism Fundamentals - MCQS Part V

Multiple Choice Questions Topic Outline

  • MCQs in Atomic Structure
  • MCQs in Electric Charge
  • MCQs in Ohm's Law, Kirchoff Law, Coulomb's Law, etc
  • MCQs in Magnetic Power
  • MCQs in Magnetic Field and Magnetic Flux
  • MCQs in Magnetic and Electric Quantities / Units
  • MCQs in Magnetic/Electromagnet Principles

The Six-Parts Series

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

Electricity and Magnetism Fundamentals 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

Start with Part V of the MCQs Series

201. Core materials of a good relay have _________ hysteresis loop.

  • A. large
  • B. narrow
  • C. very large
  • D. very narrow

202. The magnetic materials should have a large hysteresis loss for one of the following applications.

  • A. Transformers
  • B. AC motors
  • C. Permanent Magnets
  • D. DC generators

203. If the magnetic material is located within a coil through which alternating current (60 Hz frequency) flows, then __________ hysteresis loops will be formed every second.

  • A. 60
  • B. 120
  • C. 30
  • D. 180

204. There are how many compounds available in nature?

  • A. 105
  • B. 1000
  • C. 300,000
  • D. Unlimited

205. Hysteresis is a phenomenon of _________ in a magnetic circuit.

  • A. setting up constant flux
  • B. lagging of H behind B
  • C. lagging B behind H
  • D. leading B ahead H

206. What is the measure of the density and sign of the electric charge at a point relative to that at some time?

  • A. Electric potential
  • B. Electric charge
  • C. Electric current
  • D. Electric intensity

207. __________ is a substance of whose molecules consist of the same kind of atom.

  • A. Mixture
  • B. Compound
  • C. Element
  • D. Isotope

208. Hipernik is an alloy containing __________ iron and __________ nickel.

  • A. 40% ; 60%
  • B. 60% ; 40%
  • C. 50% ; 50%
  • D. 70% ; 30%

209. The mass of proton is __________ the mass of an electron.

  • A. equal to
  • B. about 1837 times
  • C. less than
  • D. 200 times

210. What is the maximum number of electrons that can be accommodated in the last orbit of an atom?

  • A. 4
  • B. 2
  • C. 8
  • D. 18

211. The electrons in the last orbit of an atom are called _______ electrons.

  • A. free
  • B. valence
  • C. bound
  • D. thermionic

212. If the number of valence electrons of an atom is less than 4, the substance is called

  • A. a conductor
  • B. a semiconductor
  • C. an insulator
  • D. a superconductor

213. If the number of valence electrons of an atom is more than 4, the substance is called

  • A. a semiconductor
  • B. a conductor
  • C. an insulator
  • D. a semi-insulator

214. If the number of valence electrons of an atom is exactly 4, then the substance is called

  • A. a semiconductor
  • B. a conductor
  • C. an insulator
  • D. a cryogenic conductor

215. If the number of valence electrons of an atom is less than 4, then the substance is probably

  • A. a metal
  • B. an insulator
  • C. a non-metal
  • D. a semiconductor

216. One coulomb of charge consists of ________ electrons.

  • A. 624 × 1016
  • B. 62.4 × 1016
  • C. 6.24 × 1016
  • D. 0.624 × 1016

217. A one cubic cm of copper has how many free electrons at room temperature?

  • A. 80 × 1018
  • B. 8.5 × 1022
  • C. 20 × 1010
  • D. 50 × 1020

218. Electronic current in a wire is the flow of ____________ electrons.

  • A. free
  • B. valence
  • C. bound
  • D. loose

219. Electromotive force in a circuit

  • A. causes free electrons to flow
  • B. increases the circuit resistance
  • C. maintains circuit resistance
  • D. is needed to make the circuit complete

220. The resistance of a material is ____________ its area of cross-section.

  • A. directly proportional
  • B. independent of
  • C. inversely proportional to
  • D. equal to

221. If the length and area of cross-section of a wire are doubled, then its resistance

  • A. becomes four times
  • B. becomes sixteen times
  • C. remains the same
  • D. becomes two times

222. A length of wire has a resistance of 10 ohms. What is the resistance of a wire of the same material three times as long and twice the cross-sectional area?

  • A. 30 ohms
  • B. 20 ohms
  • C. 15 ohms
  • D. 7 ohms

223. What is the SI unit of specific resistance or resistivity?

  • A. Ohm-circular mil per inch
  • B. Ohm-circular mil per foot
  • C. Ohm-m
  • D. Ohm-cm

224. The resistivity of a conductor ___________ with an increase in temperature.

  • A. increases
  • B. decreases
  • C. remains the same
  • D. becomes zero

225. What is the SI unit of conductance?

  • A. Siemens
  • B. Mhos
  • C. Ohms
  • D. 1/Ohms

226. If the resistance of a material 2 m long and 2 m2 in area of cross-section is 1.6 ×10-8 Ω, then its resistivity is

  • A. 3.2 × 10-8 Ω-m
  • B. 1.6 × 10-8 Ω-m
  • C. 0.64 × 10-8 Ω-m
  • D. 0.16 × 10-8 Ω-m

227. What is the SI unit of conductivity?

  • A. Ohms/m
  • B. Ohms-m
  • C. Siemens-m
  • D. Siemens/m

228. The temperature coefficient of resistance of conductors is

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

229. The temperature coefficient of resistance of semiconductors is

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

230. What determines the value of the temperature coefficient of resistance of a material?

  • A. length
  • B. cross-sectional area
  • C. volume
  • D. nature and temperature

231. The temperature coefficient of resistance of a conductor ______ with an increase in temperature.

  • A. increases
  • B. decreases
  • C. remains the same
  • D. becomes negative

232. The temperature coefficient of resistance of insulators is

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

233. The temperature coefficient of resistance of eureka is

  • A. positive
  • B. negative
  • C. almost zero
  • D. infinite

234. If the value of α0 a conductor is 1/234 per oC, then the value of α18 is

  • A. 1/218 per oC
  • B. 1/252 per oC
  • C. 1/272 per oC
  • D. 1/273 per oC

235. If the value of α25 a conductor is 1/255 per oC, then the value of α20 is

  • A. 1/300 per oC
  • B. 1/250 per oC
  • C. 1/230 per oC
  • D. 1/260 per oC

236. If the value of α25 of a conductor is 1/230 per oC, then the value of α0 is

  • A. 1/180 per oC
  • B. 1/150 per oC
  • C. 1/280 per oC
  • D. 1/230 per oC

237. Ohm’s law cannot be applied to which material?

  • A. Copper
  • B. Silver
  • C. Silicon carbide
  • D. Aluminum

238. What is the practical unit of electrical energy?

  • A. Watt
  • B. Kilowatt-hour
  • C. Kilowatt-second
  • D. Megawat-hour

239. A 200-watt lamp working for 24 hours will consume approximately _____ units.

  • A. 50
  • B. 5
  • C. 24
  • D. 0.5

240. The hot resistance of an incandescent lamp is about _______ its cold resistance.

  • A. 10 times
  • B. 100 times
  • C. 5 times
  • D. 50 times

241. Under ordinary conditions, a body is considered

  • A. positively charged
  • B. neutral
  • C. negatively charged
  • D. stable

242. A positively charged body has

  • A. deficit of electrons
  • B. excess of neutrons
  • C. excess of electrons
  • D. deficit of protons

243. A negatively charge body has

  • A. deficit of electrons
  • B. excess of protons
  • C. excess of electrons
  • D. deficit of neutrons

244. This paper does not exhibit electricity because it contains the same number of

  • A. protons and electrons
  • B. neutrons and electrons
  • C. neutrons and positrons
  • D. atoms

245. What is the value of the absolute permittivity of air?

  • A. 8.854 μF/m
  • B. 8.854 × 10-12 mF/m
  • C. 8.854 × 10-12 F/m
  • D. 8.854 × 10-12 μF/m

246. What is the relative permittivity of air?

  • A. 0
  • B. 1
  • C. 8.854 × 10-12
  • D. 4π × 10-7

247. If two similar charges 1 coulomb each are placed 1 m apart in air, then the force of repulsion is

  • A.8 × 106 N
  • B. 9 × 109 N
  • C. 106 N
  • D. 5 × 106 N

248. If the relative permittivity of a material is 10, then its permittivity is

  • A. 4π × 10^-7 F/m
  • B. 4π × 10^-6 F/m
  • C. 8.854 × 10^-11 F/m
  • D. 8.854 × 10^-12 F/m

249. The force between two charges placed a given distance apart ______ as the relative permittivity of the medium is increased.

  • A. increases
  • B. decreases
  • C. remains unchanged
  • D. becomes infinite

250. What is another name for relative permittivity?

  • A. Dielectric strength
  • B. Electric intensity
  • C. Potential gradient
  • D. Dielectric constant

NOTE:

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