Mechanical Engineering MCQs

Kirchhoff’s law states that

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the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature
the wave length corresponding to the maximum energy is proportional to the absolute temperature
the ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body
none of the above
✅ The correct answer is option C.

The moment of a force

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is the turning effect produced by a force, on the body, on which it acts
is equal to the product of force acting on the body and the perpendicular distance of a point and the line of action of the force
is equal to twice the area of the traingle, whose base is the line representing the force and whose vertex is the point, about which the moment is taken
all of the above
✅ The correct answer is option D.

The principal function of a stop valve is to

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control the flow of steam from the boiler to the main pipe and to shut off the steam completely when required
empty the boiler when required and to discharge the mud, scale or sediments which are accumulated at the bottom of the boiler
put off fire in the furnace of the boiler when the level of water in the boiler falls to an unsafe limit
increase the temperatu
✅ The correct answer is option A.