761. Damage to metal surface by mechanical action is called
A. Pitting
B. Corrosion
C. Erosion
D. None of these
✅ The correct answer is option C.
763. The stress at which a metal fails by fatigue lies
A. Near the fracture point of the stress-strain curve
B. In the plastic range
C. In the elastic range
D. None of these
✅ The correct answer is option C.
765. Fibre glass is a composite material of
A. Glass fibre in a polymer matrix
B. Glass fibre in a metallic matrix
C. Polymer fibre in a glassy matrix
D. Both B & C
✅ The correct answer is option A.
767. Diamagnetic materials
A. Are magnetised by eddy currents only
B. Are non-magnetic and can not be magnetised
C. Are magnetised in direction opposite to the magnetic field
D. Can be magnetised in one direction only
✅ The correct answer is option C.
769. What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m². °K ? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively.
A. 2
B. 5
C. 10
D. 20
✅ The correct answer is option A.
771. Thermal conductivity of a material does not depend upon its
A. Mass
B. Volume
C. Surface area
D. All of the above
✅ The correct answer is option D.
773. __________ cycle is the most efficient thermodynamic cycle.
A. Diesel
B. Otto
C. Rankine
D. Carnot
✅ The correct answer is option D.
775. Which of the following absorbs maximum heat in a high pressure boiler ?
A. Economiser
B. Steam superheater
C. Air preheater
D. Furnace water wall
✅ The correct answer is option D.
777. Multistage compression of air as compared to single stage compression offers the advantage of
A. Power saving per unit weight of air delivered
B. Moisture elimination in the inter-stage cooler
C. Increased volumetric efficiency
D. All of the above
✅ The correct answer is option D.
742. Production of a hollow product by inflation of a tube or parison is called the __________ process.
A. Blow moulding
B. Calendering
C. Extrusion
D. Injection
✅ The correct answer is option A.