Heat and Mass Transfer MCQs

Question 1

The thermal diffusivities for solids are generally

Accepted Answer

More or less same as for liquids and gases

Answer

Less than those for gases

Answer

Less than those for liquids

Answer

More than those for liquids and gases

Question 2

Heat transfer by radiation mainly depends upon

Accepted Answer

All of the above

Answer

Its temperature

Answer

Nature of the body

Answer

Kind and extent of its surface

Question 3

The transfer of heat by molecular collision is known as

Accepted Answer

Convection

Answer

Conduction

Answer

Radiation

Answer

None of these

Question 4

According to Kirchoff's law, the ratio of emissive power to absorptivity for all bodies is equal to the emissive power of a

Accepted Answer

Black body

Answer

Grey body

Answer

Brilliant white polished body

Answer

Red hot body

Question 5

40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is

Accepted Answer

0.45

Answer

0.55

Answer

0.4

Answer

0.75

Question 6

The heat transfer takes place according to

Accepted Answer

Second law of thermodynamics

Answer

Zeroth law of thermodynamics

Answer

First law of thermodynamics

Answer

Kirchhoff's law

Question 7

In case of liquids and gases, the heat transfer takes place according to

Accepted Answer

Convection

Answer

Conduction

Answer

Radiation

Answer

None of these

Question 8

Depending on the radiating properties, a body will be opaque when

Accepted Answer

x = 0, a + p = 1

Answer

p = 0, x = 0 and a = 1

Answer

p = 1, x = 0 and a = 0

Answer

p = 0, x = 1 and a = 0

Question 9

Log mean temperature difference in case of counter flow compared to parallel flow will be

Accepted Answer

More

Answer

Same

Answer

Less

Answer

Depends on other factors