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410+ Engineering Physics Solved MCQs
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Uncategorized topics .
| 251. |
According to Indian Standards, overall thermal transmittance of a wall should not be more than kcal/m2 h deg C. |
| A. | 1.3 |
| B. | 2.2 |
| C. | 3.7 |
| D. | 4.6 |
| Answer» B. 2.2 | |
| Explanation: according to indian standards, overall thermal transmittance of a wall should not be more than 2.2 kcal/m2 h deg c. heat insulation of exposed walls can be achieved by increasing the thickness of the wall. | |
| 252. |
What is solar water heater? |
| A. | use solar energy to heat water |
| B. | use solar energy to generate current which is then used to heat water |
| C. | use water to generate heat |
| D. | use solar energy to generate steam |
| Answer» A. use solar energy to heat water | |
| Explanation: solar water heater is a system that converts sunlight into heat. this heat is then used to heat water. as the water gets heated, steam may be produced but the purpose of solar water is to heat water and not produce steam. it does not generate current. | |
| 253. |
Which of the following determines complexity and size of solar water heating system? |
| A. | food |
| B. | changes in ambient temperature |
| C. | chemicals |
| D. | solar radiation constant |
| Answer» B. changes in ambient temperature | |
| Explanation: changes in ambient temperature during day-night cycle is one of the factors that determines the complexity and size of solar water heating system. food, chemicals and solar radiation constant does not influence the complexity and size of the system. | |
| 254. |
What is freeze protection in a solar water heating system? |
| A. | ensures that the system is frozen |
| B. | prevents the operation of drainback system |
| C. | prevents damage to system due to freezing of transfer fluid |
| D. | ensures that the transfer fluid is frozen |
| Answer» C. prevents damage to system due to freezing of transfer fluid | |
| Explanation: freeze protection in a solar water system prevents the system being damaged due to freezing of transfer fluid. it does not prevent the operation of drainback system. | |
| 255. |
What are drainback systems in solar water heating system? |
| A. | the system that reverses the direction of flow of transfer fluid |
| B. | the system that tracks the sun |
| C. | the system that pumps excess transfer fluid |
| D. | the system that drains the transfer fluid |
| Answer» D. the system that drains the transfer fluid | |
| Explanation: drainback systems are systems that drain the transfer fluid particularly to ensure freeze protection. this prevents the freezing of transfer fluid and any unwanted damage to the system. | |
| 256. |
How does freeze-tolerance work? |
| A. | by expansion of pipes carrying transfer fluid |
| B. | by compression of pipes carrying transfer fluid |
| C. | by increasing the temperature of pipes carrying transfer fluid |
| D. | by increasing the pressure inside pipes carrying transfer fluid |
| Answer» A. by expansion of pipes carrying transfer fluid | |
| Explanation: freeze-tolerance works by expansion of pipes carrying the transfer fluid. the low pressure pipes are made of silicone rubber that expands on freezing. | |
| 257. |
Which of the following metals are used to make pipes of low cost solar water heating system? |
| A. | gold |
| B. | copper |
| C. | polymer |
| D. | silver |
| Answer» B. copper | |
| Explanation: copper is used to make pipes of low cost solar water heating systems. | |
| 258. |
Direct solar water heating systems |
| A. | offer great overheating protection |
| B. | are called pumped systems |
| C. | offer no overheating protection |
| D. | offer great freeze protection |
| Answer» C. offer no overheating protection | |
| Explanation: direct solar water heating systems are also called compact systems. they offer little or no overheating protection unless they have a heat export pump. | |
| 259. |
How is the heat transferred from transfer fluid to potable water in indirect solar water heating systems? |
| A. | by directly exposing the substance to sunlight |
| B. | by using an electrical heater |
| C. | by circulating potable water through the collector |
| D. | by using heat exchanger |
| Answer» D. by using heat exchanger | |
| Explanation: an indirect solar water heating system uses a heat exchanger to transfer heat from the transfer fluid to the potable water. it does not expose the transfer fluid directly to the sunlight and does not use an electrical heater. | |
| 260. |
How is water heated in a direct solar water heating system? |
| A. | by circulating potable water through the collector |
| B. | by directly exposing water to sunlight |
| C. | by using convection from a different transfer fluid |
| D. | by using heat exchanger |
| Answer» A. by circulating potable water through the collector | |
| Explanation: in a direct solar water heating system, the potable water is the transfer fluid. hence, it is heated by circulating through the collector. indirect solar water heating systems use a heat exchanger. | |
| 261. |
Passive systems rely on heat-driven convection. |
| A. | false |
| B. | true |
| Answer» B. true | |
| Explanation: passive systems rely on heat- driven convection. if not, they also use heat pipes to circulate the working fluid through the collector and heat it. hence, they are cheap and are easily maintained. | |
| 262. |
Which of the following is an example of direct solar water heating system? |
| A. | pressurised antifreeze system |
| B. | pumped systems to circulate transfer fluid |
| C. | convection heat storage system |
| D. | drainback system |
| Answer» C. convection heat storage system | |
| Explanation: convection heat storage system is similar to an integrated collector storage system. both these systems are examples of direct solar water heating systems. | |
| 263. |
How is the heat transfer fluid (HTF) heated in bubble pump systems? |
| A. | by subjecting the closed htf circuit to high pressure |
| B. | by subjecting the closed htf circuit to high pressure and by increasing the volume |
| C. | by subjecting the closed htf circuit to low pressure and by decreasing the volume |
| D. | by subjecting the closed htf circuit to low pressure |
| Answer» D. by subjecting the closed htf circuit to low pressure | |
| Explanation: in a bubble pump system, the heat transfer fluid circuit is subjected to a low pressure. this causes the liquid to boil at low temperatures as the sun heats it. the volume is not changed. | |
| 264. |
Batch collectors reduce heat loss by thermally insulating the storage tank. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: batch collectors reduce heat | |
| 265. |
Overheat protection is done by passing hot water through collector during night. |
| A. | false |
| B. | true |
| Answer» B. true | |
| Explanation: overheat protection is done by passing hot water through collector during night or when there is less sunlight. this is extremely effective in direct or thermal store plumbing and ineffective in evacuated-tube collectors. | |
| 266. |
As the wavelength of the radiation decreases, the intensity of the black body radiations |
| A. | increases |
| B. | decreases |
| C. | first increases then decrease |
| D. | first decreases then increase |
| Answer» C. first increases then decrease | |
| Explanation: in the case of black body radiations, as the body gets hotter the wavelength of the emitted radiation decreases. however, the intensity first increases up to a specific wavelength than starts decreasing, as the wavelength continues to decrease. | |
| 267. |
The radiations emitted by hot bodies are called as |
| A. | x-rays |
| B. | black-body radiation |
| C. | gamma radiations |
| D. | visible light |
| Answer» B. black-body radiation | |
| Explanation: the phenomenon of black— body radiations was given by max planck. he stated that hot bodies emit radiation over a wide range of wavelengths. an ideal body is the one that emits and absorbs radiation of all frequencies. such a body called a black body and the radiations are called black body radiations. | |
| 268. |
An iron rod is heated. The colors at different temperatures are noted. Which of the following colors shows that the iron rod is at the lowest temperature? |
| A. | red |
| B. | orange |
| C. | white |
| D. | blue |
| Answer» A. red | |
| Explanation: as the body gets hotter, the frequency of the emitted radiation keeps on increasing. blue color has the highest frequency out of red, orange and white. thus, as the iron rod gets heated first it would become red, then orange, then white and then finally blue. | |
| 269. |
A black body is defined as a perfect absorber of radiations. It may or may not be a perfect emitter of radiations. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: a black body is defined as the one which is a perfect absorber as well as a perfect emitter of radiations. such a body would absorb all the radiations falling on it and would emit all of them when heated. | |
| 270. |
From the figure, what’s the relation between T1, T2, and T3?
|
| A. | t1 > t2 > t3 |
| B. | t3 > t2 > t2 |
| C. | t3 > t1 > t2 |
| D. | t2 > t1 > t3 |
| Answer» B. t3 > t2 > t2 | |
| Explanation: we already know, as the temperature of the body is higher, the intensity of the black body radiations would be higher. thus, from the graph, the radiations with temperature t3 has the highest intensity followed by the one with temperature t2 and then t1. thus, t3> t2 > t1. | |
| 271. |
Electromagnetic wave theory of light could not explain Black Body radiations. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: according to electromagnetic theory, the absorption and the emission should be continuous. as the wavelength keeps decreasing, the intensity of the emitted radiations should keep increasing to infinity. such is not the case with black body radiations. | |
| 272. |
The unit of absorptive power is |
| A. | t |
| B. | ts-1 |
| C. | ts |
| D. | no unit |
| Answer» D. no unit | |
| Explanation: absorptive power can be defined as the ratio of energy absorbed per unit area upon energy incident per unit time per unit area. for a black body, it’s absorptive power is equal to one. | |
| 273. |
For an object other than a black body, it’s emissivity, e is |
| A. | 1 |
| B. | 0 < e < 1 |
| C. | e > 1 |
| D. | e = 0 |
| Answer» B. 0 < e < 1 | |
| Explanation: emissivity is the ratio of emissive power of any object and the emissive power of the black body having the same temperature and surface area as the object. thus, for a black body, it is equal to 1. for any other object, it is less than 1. | |
| 274. |
What relation between emissivity, e, and Absorptive Power, a, is given by Kirchhoff’s law? |
| A. | e < a |
| B. | e > a |
| C. | e = a |
| D. | no specific relation |
| Answer» C. e = a | |
| Explanation: kirchhoff’s law states that for any object the emissivity is always equal to absorptive power. for a black body, both of them are equal to one. | |
| 275. |
What is the relation between the Energies as shown in the figure? |
| A. | er = 0 |
| B. | ea = 0 |
| C. | et = ei |
| D. | ei = er |
| Answer» A. er = 0 | |
| Explanation: as a black body is a perfect absorber, the reflected energy and the transmitted energy should be zero. also, the energy of the incident radiation should be equal to the energy absorbed. | |
| 276. |
The energy emitted by a black surface should not vary in accordance with |
| A. | wavelength |
| B. | temperature |
| C. | surface characteristics |
| D. | time |
| Answer» D. time | |
| Explanation: it is time independent. for a prescribed wavelength, the body radiates much more energy at elevated temperatures. | |
| 277. |
2 PLANCK'S THEORY (DERIVATION) |
| A. | a sin α |
| B. | a cos α |
| C. | 2a cos α |
| D. | 2a cos α |
| Answer» B. a cos α | |
| Explanation: the solid angle is defined by a region by the rays of a sphere, and is measured as a n/r2. | |
| 278. |
Likewise the amount of emitted radiation is strongly influenced by the wavelength even if temperature of the body is |
| A. | constant |
| B. | increasing |
| C. | decreasing |
| D. | it is not related with temperature |
| Answer» A. constant | |
| Explanation: temperature must remain constant in order to emit radiation. | |
| 279. |
5 kW/m2. Determine the wavelength of emission maximum |
| A. | 8.46 micron m |
| B. | 7.46 micron m |
| C. | 6.46 micron m |
| D. | 5.46 micron m |
| Answer» D. 5.46 micron m | |
| Explanation: (wavelength) max t = 2.8908 * 10 -3. | |
| 280. |
The sun emits maximum radiation of 0.52 micron meter. Assuming the sun to be a black body, Calculate the emissive ability of the sun’s surface at that temperature |
| A. | 3.47 * 10 7 w/m2 |
| B. | 4.47 * 10 7 w/m2 |
| C. | 5.47 * 10 7 w/m2 |
| D. | 6.47 * 10 7 w/m2 |
| Answer» C. 5.47 * 10 7 w/m2 | |
| Explanation: e = σ b t 4 = 5.47 * 10 7 w/m2. | |
| 281. |
The law governing the distribution of radiant energy over wavelength for a black body at fixed temperature is referred to as |
| A. | kirchhoff’s law |
| B. | planck’s law |
| C. | wein’s formula |
| D. | lambert’s law |
| Answer» B. planck’s law | |
| Explanation: this law gives a relation between energy over wavelength. | |
| 282. |
The Planck’s constant h has the dimensions equal to |
| A. | m l 2 t -1 |
| B. | m l t -1 |
| C. | m l t -2 |
| D. | m l t |
| Answer» A. m l 2 t -1 | |
| Explanation: it has unit equal to j s and its value is 6.626 * 10 -34. | |
| 283. |
A furnace emits radiation at 2000 K. Treating it as a black body radiation, calculate the monochromatic radiant flux density at 1 micron m wavelength |
| A. | 5.81 * 10 7 w/m2 |
| B. | 4.81 * 10 7 w/m2 |
| C. | 3.81 * 10 7 w/m2 |
| D. | 2.81 * 10 7 w/m2 |
| Answer» D. 2.81 * 10 7 w/m2 | |
| Explanation: (e) b = c 1 (wavelength) | |
| 284. |
A metal sphere of surface area 0.0225 m2 is in an evacuated enclosure whose walls are held at a very low temperature. Electric current is passed through resistors embedded in the sphere causing electrical energy to be dissipated at the rate of 75 W. If the sphere surfaces temperature is measured to be 560 K, while in steady state, calculate emissivity of the sphere surface |
| A. | 0.498 |
| B. | 0.598 |
| C. | 0.698 |
| D. | 0.798 |
| Answer» B. 0.598 | |
| Explanation: e = e a σ b t. | |
| 285. |
Which of the following is the characteristic of a black body? |
| A. | a perfect absorber but an imperfect radiator |
| B. | a perfect radiator but an imperfect absorber |
| C. | a perfect radiator and a perfect absorber |
| D. | a perfect conductor |
| Answer» C. a perfect radiator and a perfect absorber | |
| Explanation: when the radiations are made | |
| 286. |
The energy distribution is not uniform for any given temperature in a perfect black body. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: at different temperatures, when a perfect black body is allowed to emit radiations, then the distribution of energy for different wavelengths at various temperatures is not uniform. | |
| 287. |
Rayleigh-Jean’s law holds good for which of the following? |
| A. | shorter wavelength |
| B. | longer wavelength |
| C. | high temperature |
| D. | high energy |
| Answer» B. longer wavelength | |
| Explanation: according to this law, the energy distribution is directly proportional to the absolute temperature and is inversely proportional to the fourth power of the wavelength. therefore longer the wavelength, greater is the energy distribution. | |
| 288. |
Wien’s displacement law holds good only for shorter wavelength. |
| A. | false |
| B. | true |
| Answer» B. true | |
| Explanation: this law states that, the product of the wavelength, corresponding to maximum energy and the absolute temperature, is constant. if ʎ is less, then 1/ʎ will be great. therefore e(hc/ʎkt) will be great. | |
| 289. |
Which of the following does not affect the photon? |
| A. | magnetic or electric field |
| B. | light waves |
| C. | gravity |
| D. | current |
| Answer» A. magnetic or electric field | |
| Explanation: photons have no charge. they can interact with charged particles but not with themselves. this is why photons are neutral and not affected by magnetic or electric fields. | |
| 290. |
What is Compton shift? |
| A. | shift in frequency |
| B. | shift in charges |
| C. | shift in radiation |
| D. | shift in wavelength |
| Answer» D. shift in wavelength | |
| Explanation: when a photon collides with an electron at rest, the photon gives its energy to the electron. therefore the scattered photon will have higher wavelength compared to the wavelength of the incident photon. this shift in wavelength is called compton shift. | |
| 291. |
Compton shift depends on which of the following? |
| A. | incident radiation |
| B. | nature of scattering substance |
| C. | angle of scattering |
| D. | amplitude of frequency |
| Answer» C. angle of scattering | |
| Explanation: from the theory of compton effect it is deducted that change in wavelength | |
| 292. |
Which of the following is called as non- mechanical waves? |
| A. | magnetic waves |
| B. | electromagnetic waves |
| C. | electrical waves |
| D. | matter waves |
| Answer» B. electromagnetic waves | |
| Explanation: the waves which travel in the form of oscillating electric and magnetic waves are called electromagnetic waves. such waves do not require any material for their propagation and are called non-mechanical waves. | |
| 293. |
Which of the following is associated with an electron microscope? |
| A. | matter waves |
| B. | electrical waves |
| C. | magnetic waves |
| D. | electromagnetic waves |
| Answer» A. matter waves | |
| Explanation: the waves associated with microscopic particles when they are in motion are called matter waves. electron microscope makes use of the matter waves associated with fast moving electrons. | |
| 294. |
A radio station broadcasts its programme at 219.3 metre wavelength. Determine the frequency of radio waves if velocity of radio waves is 3×108 m/s. |
| A. | 7.31×10-7 hz |
| B. | 1.954×10-6 hz |
| C. | 1.368×106 hz |
| D. | 6.579×1010 hz |
| Answer» C. 1.368×106 hz | |
| Explanation: ʎ = velocity/frequency frequency = velocity/ʎ | |
| 295. |
Calculate the de-Broglie wavelength of an electron which has been accelerated from rest on application of potential of 400volts. |
| A. | 0.1653 Å |
| B. | 0.5125 Å |
| C. | 0.6135 Å |
| D. | 0.2514 Å |
| Answer» C. 0.6135 Å | |
| Explanation: de-broglie wavelength = h/ | |
| 296. |
When a pebble is dropped into a pond of still water, what happens? |
| A. | particles move |
| B. | waves move |
| C. | the pebble moves |
| D. | water moves |
| Answer» B. waves move | |
| Explanation: when a pebble is thrown in still water, a circular pattern of alternate crests spread out. the kinetic energy makes the particles to oscillate which comes in contact with it. the energy gets transferred to the particles of the next layer which also begins to oscillate. thus it is the disturbance or waves that move forward and not the particles of the medium. | |
| 297. |
Mechanical waves are called elastic waves. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: waves which require a medium for their propagation are called mechanical waves. they are also called elastic waves because they depend on the elastic properties of a medium. | |
| 298. |
What are the essential properties a medium must possess for the propagation of mechanical waves? |
| A. | stable pressure |
| B. | maximum friction |
| C. | constant temperature |
| D. | minimum friction |
| Answer» D. minimum friction | |
| Explanation: the friction force amongst the particles of the medium should be negligibly small so that they continue oscillating for a sufficiently long time and the wave travels a sufficiently long distance through the medium | |
| 299. |
Transverse waves can be formed in fluids. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: transverse waves travel in the form of crests and troughs. they involve changes in the shape of the medium. so they can be transmitted through media which have rigidity. as fluids do not sustain shearing stress, transverse waves cannot be formed in them. | |
| 300. |
Which of the following waves can be transmitted through solids, liquids and gases? |
| A. | transverse waves |
| B. | electromagnetic waves |
| C. | mechanical waves |
| D. | longitudinal waves |
| Answer» D. longitudinal waves | |
| Explanation: longitudinal waves involve changes in the volume and density of the medium. since all media can sustain compressive stress, longitudinal waves can be transmitted through all the three types of media. | |
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