61⟩ There is no hysteresis phenomenon is any dielectric material. A. True B. False
Option B
(False)
Explanation:
Hysteresis phenomenon exists in dielectric materials.
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82 Engineering Questions And Answers
62⟩ A copper atom is neutral. Its core has a net charge of A. 0 B. + 1 C. - 1 D. + 2
Option B
(+ 1)
63⟩ The attraction between the nucleus and valence electron of copper atom is A. zero B. weak C. strong D. either zero or strong
Option B
(weak)
Explanation:
The valence electron, in copper atom, can be easily detached from nucleus.
64⟩ Diamagnetic materials do not have permanent magnetic dipoles. A. True B. False
Option A
(True)
65⟩ A piece of copper and another piece of Germanium are cooled from 30°C to 80 K. The resistance of A. copper decreases and germanium increases B. both decreases C. both increases D. copper increases and germanium decreases
Option A
(copper decreases and germanium increases)
Explanation:
As temperature is decreased, resistance of conductors decreases and resistance of semiconductors increases.
66⟩ The units for electric dipole moment are A. coulombs B. colomb-metre C. coulomb/metre
Option B
(colomb-metre)
Explanation:
It is product of charge and distance.
67⟩ The temperature coefficient of resistivity of semiconductors is A. positive B. negative C. may be positive or negative D. very low
Option B
(negative)
Explanation:
Resistance of semiconductors decreases with increase in temperature.
68⟩ Which of the following is used in automatic control of street lights? A. Thermistor B. Photo-conductor C. Transistor D. Varistor
Option B
(Photo-conductor)
69⟩ The current flow in a semiconductor is due to A. holes B. electrons C. holes and electrons D. holes, electrons and ions
Option C
(holes and electrons)
70⟩ A good dielectric should have A. low losses B. good heat conductivity C. high intrinsic strength D. all of the above
Option D
(all of the above)
71⟩ Magnetic hysteresis phenomenon is explained by A. motion of domain walls B. motion of domain walls and domain rotation C. domain rotation D. none of the above
Option B
(motion of domain walls and domain rotation)
72⟩ What is heat treatment?
Heat treatment can be defined as a combination of processes or operations in which the heating and cooling of a metal or alloy is done in order to obtain desirable characteristics without changing the compositions. Some of the motives or purpose of heat treatment are as follows:
☛ In order to improve the hardness of metals.
☛ For the softening of the metal.
☛ In order to improve the mach-inability of the metal.
☛ To change the grain size.
☛ To provide better resistance to heat, corrosion, wear etc.
73⟩ Explain rules for designing castings?
☛ To avoid the concentration of stresses sharp corners and frequent use of fillets should be avoided.
☛ Section thicknesses should be uniform as much as possible. For variations it must be done gradually.
☛ Abrupt changes in the thickness should be avoided at all costs.
☛ Simplicity is the key, the casting should be designed as simple as possible.
☛ It is difficult to create true large spaces and henceforth large flat surfaces must be avoided.
☛ Webs and ribs used for stiffening in castings should as minimal as possible.
☛ Curved shapes can be used in order to improve the stress handling of the cast.
74⟩ What you know about Engineering?
Engineering word is derived from Latin ingenium, meaning "cleverness" and ingeniare, meaning "to contrive, devise" is the application of scientific, economic, social, and practical knowledge in order to invent, design, build, maintain, research, and improve structures, machines, devices, systems, materials and processes.
75⟩ Explain the disciplines of engineering?
The discipline of engineering is extremely broad, and encompasses a range of more specialized fields of engineering, each with a more specific emphasis on particular areas of applied science, technology and types of application.
76⟩ Why generally performed heat treatment?
Heat treatment is generally performed in the following ways:
☛ Normalizing
☛ Annealing
☛ Spheroidising
☛ Hardening
☛ Tempering
☛ Surface or case hardening
77⟩ Who is Engineer?
An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics, and ingenuity to develop solutions for technical, societal and commercial problems. Engineers design materials, structures, and systems while considering the limitations imposed by practicality, regulation, safety, and cost.
78⟩ What is LNG (Liquefied Natural Gas)?
LNG (Liquefied Natural Gas) is natural gas stored as a super-cooled (cryogenic) liquid. The temperature required to condense natural gas depends on its precise composition, but it is typically between -120 and -170°C (-184 and -274°F). The advantage of LNG is that it offers an energy density comparable to petrol and diesel fuels, extending range and reducing refueling frequency.
79⟩ What is CNG (Compressed Natural Gas)?
Compressed Natural Gas or CNG is stored on the vehicle in high-pressure tanks - 20 to 25 MPa (200 to 250 bar, or 3,000 to 3,600 psi). Natural gas consists mostly of methane and is drawn from gas wells or in conjunction with crude oil production. As delivered through the pipeline system, it also contains hydrocarbons such as ethane and propane as well as other gases such as nitrogen, helium, carbon dioxide, sulphur compounds, and water vapour. A sulphur-based odourant is normally added to CNG to facilitate leak detection. Natural gas is lighter than air and thus will normally dissipate in the case of a leak, giving it a significant safety advantage over gasoline or LPG.
80⟩ What is LPG (Liquefied Petroleum Gas)?
Liquefied Petroleum Gas or LPG (also called Autogas) consists mainly of propane, propylene, butane, and butylene in various mixtures. It is produced as a by-product of natural gas processing and petroleum refining. The components of LPG are gases at normal temperatures and pressures. One challenge with LPG is that it can vary widely in composition, leading to variable engine performance and cold starting performance. At normal temperatures and pressures, LPG will evaporate. Because of this, LPG is stored in pressurized steel bottles. Unlike natural gas, LPG is heavier than air, and thus will flow along floors and tend to settle in low spots, such as basements. Such accumulations can cause explosion hazards, and are the reason that LPG fueled vehicles are prohibited from indoor parkades in many jurisdictions.
