Engineering MCQs

Which of the following is the correct statement of the second law of thermodynamics?

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It is impossible to construct an engine working on a cyclic process, whose sole purpose is to convert heat energy into work.
It is impossible to transfer heat from a body at a lower temperature to a higher temperature, without the aid of an external source.
There is a definite amount of mechanical energy, which can be obtained from a given quantity of heat energy.
all of the above
✅ The correct answer is option D.

The equivalent evaporation is defined as

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the ratio of heat actually used in producing the steam to the heat liberated in the furnace
the amount of water evaporated or steam produced in kg per kg of fuel burnt
the amount of water evaporated from and at 100° C into dry and saturated steam
the evaporation of 15.
✅ The correct answer is option C.

In a steam engine, one method of obtaining the earlier cut-off with a simple slide valve is by increasing the angle of advance of the eccentric while the throw of the eccentric, steam lap and exhaust lap are kept constant. This method will

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cause withdrawing or throttling of steam
reduce length of effective stroke of piston
reduce maximum opening of port to steam
all of these
✅ The correct answer is option B.

Which of the following statement is correct regarding petrol engines?

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A fine fuel spray mixed with air is ignited by the heat of compression which is at a high pressure.
The fuel supplied to the engine cylinder is mixed with necessary amount of air and the mixture in ignited with the help of a spark plug.
The fuel is first evaporated after passing through a carburettor and is mixed with air before ignition.
all of the above
✅ The correct answer is option B.