1) Mining industry usually employs following motive power___________________? a. A.C. electric motor b. compressed air c. petrol engine d. diesel engine e. D.C. electric motor
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2) Separators in compressor installations are located_____________________? a. before intercooler b. after intercooler c. after receiver d. between after-cooler and air receiver e. before suction
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3) An air compressor may be controlled by____________________? a. throttle control B. clearance control b. blow-off control c. any one of the above d. none of the above
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4) During peak load periods, the best method of controlling compressors is___________________? a. start-stop motor b. constant speed unloader c. relief valve d. variable speed e. none of the above
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5) The compressor performance at higher altitude compared to sea level will be _______________? a. same b. higher c. lower d. dependent on other factors e. none of the above
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6) A centrifugal compressor works on the principle of__________________? a. conversion of pressure energy into kinetic energy b. conversion of kinetic energy into pres¬sure energy c. centripetal action d. generating pressure directly e. combination of A. and D.
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7) A compressor at high altitude will draw________________? a. more power b. less power c. same power d. more/less power depending on other factors e. none of the above
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8) The thrust on the rotor in a centrifugal compressor is produced by________________? a. radial component b. axial component c. tangential component d. resultant component
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9) The area of actual indicator diagram on an air compressor as compared to area of ideal indicator diagram is_____________________? a. less b. more c. same d. more/less depending on compressor capacity e. unpredictable
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10) To aviod moisture troubles, the compressed air main line should __________________? a. rise gradually towards the point of use b. drop gradually towards the point of use c. be laid vertically d. be laid exactly horizontally e. none of the above
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11) To avoid moisture troubles, the branch connections from compressed air lines should be taken from_________________? a. top side of main b. bottom side of main c. left side of main d. right side of main e. any location
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12) For a compressor, least work will be done if the compression is________________ ? a. isentropic b. isothermal c. polytropic d. somewhere in between isentropic and isothermal e. none of the above
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13) The compressor efficiecny is the__________________? a. isothermal H.P/indicated H.R b. isothermal H.P./shaft H.R c. total output/air input d. compression work/motor input e. none Of the above
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14) For slow-speed large capacity compressor, following type of valve will be best suited________________? a. poppet valve b. mechanical valve of the corliss, sleeve, rotary or semirotary type c. disc or feather type d. any of the above e. none of the above
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15) The volumetirc efficiency of a compressor is calculated on the basis of __________________? a. volume of air inhaled at working conditions b. volume of air inhaled at N.T.P. conditions c. volume at 0°C and 1 kg/cm2 d. volume at 20°C and 1 kg/cm2 e. none of the above
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16) During base load operation, the best method of controlling compressor is ___________________? a. start-stop motor b. constant speed unloader c. relief valve d. variable speed e. none of the above
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17) The volumetric efficiency of a compressor falls roughly as follows for every 100 m increase in elevation___________________? a. 0.1% b. 0.5% c. 1.0% d. 5% e. 10%.
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18) In a compressor, free air delivered is the actual volume delivered at the stated pressure reduced to ____________________? a. N.T.P. conditions b. intake temperature and pressure conditions c. 0°C and 1 kg/cm2 d. 20°C and 1 kg/cm2 e. none of the above
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19) The advantage of multistage compression over single stage compression is ________________? a. lower power consumption per unit of air delivered b. higher volumetric efficiency c. decreased discharge temperature d. moisture free air e. all of the above
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20) As the value of index ‘«’ is decreased, the volumetric efficiency will___________________? a. increase b. decrease c. remain unaffected d. may increase/decrease depending on compressor clearance e. none of the above
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