# Heat & Mass Transfer MCQ - Multiple Choice Question and Answer

## Heat & Mass Transfer MCQ with detailed explanation for interview, entrance and competitive exams. Explanation are given for understanding.

Question No : 15
Heat flows from one body to other when they have

Different heat contents
Different specific heat
Different atomic structure
Different temperatures

Question No : 16
The rate of heat flow through a body is Q = [kA (T₁ - T₂)]/x. The term x/kA is known as

Thermal coefficient
Thermal resistance
Thermal conductivity
None of these

Question No : 17
A perfect black body is one which

Is black in colour
Reflects all heat
Absorbs heat radiations of all wave lengths falling on it

Question No : 18
Planck's law holds good for

Black bodies
Polished bodies
All coloured bodies
All of the above

Question No : 19
In counter flow heat exchangers

Both the fluids at inlet (of heat exchanger where hot fluid enters) are in their coldest state
Both the fluids at inlet are in their hottest state
Both the fluids at exit are in their hottest state
One fluid is in hottest state and other in coldest state at inlet

Question No : 20
The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number) n, where n is equal to

-1/3
-2/3
1
-1

Question No : 21
The thermal diffusivities for solids are generally

Less than those for gases
Less than those for liquids
More than those for liquids and gases
More or less same as for liquids and gases