311. Which of the following is the most suitable abrasive for grinding high tensile strength materials ?
A. Silicon carbide
B. Corundum
C. Aluminium oxide
D. Boron carbide

312. The noble metals________________?
A. Are exemplified by Na, K and Li
B. Do not resist corrosion very strongly
C. Are the lowermost in the electro-chemical series of metals
D. None of these

313. Unit of surface tension in S.I. unit is_________________?
A. Watt/m
B. Joule/m2
C. Newton/m2
D. Joule/m

314. Co-efficient of performance of a Carnot cycle refrigerator operating between – 23°C and + 27°C is ________________?
A. 3
B. 5
C. 0.5
D. 1.5

315. Lead is poured into the joint between two _______________ pipes ?
A. Mild steel
B. Concrete
C. Cast iron
D. Asbestos cement

316. ______________ circuit is most commonly used to measure strain with the help of a strain gauge?
A. Ballast
B. Voltage balancing potentiometric
C. Simple current sensitive
D. None of these

317. Basic open hearth furnace (BOF) is not used for producing ______________ steel?
A. Killed
B. Rimming
C. High alloy
D. None of these

318. Laser is a device to produce___________________?
A. Gamma rays
B. Microwaves
C. A beam of white light
D. A beam of coherent light

319. Which of the following is the most wear resistant grade of carbide used for the cutting tools ?
A. Aluminium carbide
B. Tungsten carbide
C. Nickel carbide
D. Iron carbide

320. Thermal efficiency of an internal combustion engine is around ______________ percent?
A. 8
B. 35
C. 65
D. 80

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