Heat and Mass Transfer MCQs

Question 1

The time constant of a thermocouple is

Accepted Answer

The time taken to attain 63.2% of the value of initial temperature difference

Answer

The time taken to attain the final temperature to be measured

Answer

The time taken to attain 50% of the value of initial temperature difference

Answer

Determined by the time taken to reach 100°C from 0°C

Question 2

The total emissivity power is defined as the total amount of radiation emitted by a black body per unit

Accepted Answer

Time

Answer

Temperature

Answer

Thickness

Answer

Area

Question 3

Heat transfer takes place as per

Accepted Answer

Second law of the thermodynamics

Answer

Zeroth law of thermodynamics

Answer

First law of thermodynamic

Answer

Kirchoff's law

Question 4

Thermal diffusivity is

Accepted Answer

A physical property of the material

Answer

A dimensionless parameter

Answer

Function of temperature

Answer

Used as mathematical model

Question 5

Unit of thermal diffusivity is

Accepted Answer

m2/hr

Answer

m2/hr °C

Answer

kcal/m2 hr

Answer

kcal/m hr °C

Question 6

Temperature of steam at around 540°C can be measured by

Accepted Answer

Thermocouple

Answer

Thermometer

Answer

Thermistor

Answer

None of these

Question 7

The total radiation from a black body per second per unit area is ________ fourth power of the absolute temperature. This statement is known as Stefan Boltzmann law.

Accepted Answer

Directly proportional to

Answer

Equal to

Answer

Inversely proportional to

Answer

None of these

Question 8

The use of heat exchangers is made in

Accepted Answer

All of the above

Answer

Radiators in automobile

Answer

Condensers and boilers in steam plants

Answer

Condensers and evaporators in refrigeration and air conditioning units

Question 9

The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. This statement is called

Accepted Answer

Newton's law of cooling

Answer

First law of thermodynamics

Answer

Newton's law of heating

Answer

Stefan's law