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| Engineering Reviewer - Electricity and Magnetism Fundamentals |
Electricity and Magnetism Fundamentals
200. Which of the following materials has the least hysteresis loop area?
A. soft iron
B. silicon steel
C. hard steel
D. wrought iron
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 × 10^16
B. 62.4 × 10^16
C. 6.24 × 10^16
D. 0.624 × 10^16
217. A one cubic cm of copper has how many free electrons at room temperature?
A. 80 × 10^18
B. 8.5 × 10^22
C. 20 × 10^10
D. 50 × 10^20
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 m^2 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 × 10^6 N
B. 9 × 10 ^9 N
C. 10^6 N
D. 5 × 10^6 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
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