Thermodynamics

Exercise: Thermodynamics

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

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

Answer: D

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In an isothermal process,

there is no change in temperature

there is no change in enthalpy

there is no change in internal energy

all of these

Answer: D

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The compression ratio for Diesel engines is

3 to 6

5 to 8

15 to 20

20 to 30

Answer: C

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The general gas energy equation is (where Q_{1 - 2} = Heat supplied, dU = Change in internal energy, and W_{1 - 2} = Work done in heat units)

Q_{1 - 2} = dU + W_{1 - 2}

Q_{1 - 2} = dU - W_{1 - 2}

Q_{1 - 2} = dU/W_{1 - 2}

Q_{1 - 2} = dU x W_{1 - 2}

Answer: A

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The dual combustion cycle consists of one constant pressure, two constant volume and two isentropic processes.

Agree

Disagree

Answer: A

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