Engineering Thermodynamics MCQs

Question 1

Otto cycle efficiency is higher than Diesel cycle efficiency for the same compression ratio and heat input because in Otto cycle

Accepted Answer

Heat rejection is lower

Answer

Expansion and compression are isentropic

Answer

Combustion is at constant volume

Answer

Maximum temperature is higher

Question 2

Which of the following processes is irreversible process?

Accepted Answer

Throttling

Answer

Isothermal

Answer

Adiabatic

Answer

All of the above

Question 3

The amount of heat required to raise the temperature of the unit mass of gas through one degree at constant volume, is called

Accepted Answer

Specific heat at constant volume

Answer

Kilo Joule

Answer

Specific heat at constant pressure

Answer

None of these

Question 4

A diathermic wall is one which

Accepted Answer

Permits thermal interaction

Answer

Prevents thermal interaction

Answer

Encourages thermal interaction

Answer

Discourages thermal interaction

Question 5

An adiabatic wall is one which

Accepted Answer

Prevents thermal interaction

Answer

Permits thermal interaction

Answer

Encourages thermal interaction

Answer

Discourages thermal interaction

Question 6

The polytropic index (n) is given by

Accepted Answer

$$\frac{{\log \left( {\frac{{{{	ext{p}}_2}}}{{{{	ext{p}}_1}}}} ight)}}{{\log \left( {\frac{{{{	ext{v}}_1}}}{{{{	ext{v}}_2}}}} ight)}}$$

Answer

$$\frac{{\log \left( {{{	ext{p}}_1}{{	ext{p}}_2}} ight)}}{{\log \left( {{{	ext{v}}_1}{{	ext{v}}_2}} ight)}}$$

Answer

$$\frac{{\log \left( {\frac{{{{	ext{v}}_1}}}{{{{	ext{v}}_2}}}} ight)}}{{\log \left( {\frac{{{{	ext{p}}_1}}}{{{{	ext{p}}_2}}}} ight)}}$$

Answer

$$\log \left( {\frac{{{{	ext{p}}_1}{{	ext{v}}_1}}}{{{{	ext{p}}_2}{{	ext{v}}_2}}}} ight)$$

Question 7

Minimum work in compressor is possible when the value of adiabatic index ‘n’ is equal to

Accepted Answer

1

Answer

0.75

Answer

1.27

Answer

1.35

Question 8

Which of the following cycles has maximum efficiency?

Accepted Answer

Carnot

Answer

Rankine

Answer

Stirling

Answer

Brayton

Question 9

No liquid can exist as liquid at

Accepted Answer

Zero pressure

Answer

273°K

Answer

Vacuum

Answer

Centre of earth