ExamVeda
Login
Home

Heat And Mass Transfer MCQ Questions & Answers | Mechanical Engineering

Learn Heat And Mass Transfer MCQ questions & answers are available for a Mechanical Engineering students to clear GATE exams, various technical interview, competitive examination, and another entrance exam. Heat And Mass Transfer MCQ question is the important chapter for a Mechanical Engineering and GATE students. Page-4 section-1

Each section contains 100 MCQs on Heat and Mass Transfer .
31
Heat conducted through per unit area and unit thick face per unit time when temperature difference between opposite faces is unity, is called
Discuss
Answer & Solution
Answer: Option D
Solution:
A measure of the ability of a material to transfer heat. Given two surfaceson either side of the material with a temperature difference between them,the thermal conductivity is the heat energy transferred per unit time andper unit surface area, divided by the temperature difference. It is measured in watts per degree Kelvin.
32
The rate of heat flow through a body is $${\text{Q}} = \frac{{{\text{kA}}\left( {{{\text{T}}_1} - {{\text{T}}_2}} \right)}}{{\text{x}}}.$$    The term $$\frac{{\text{x}}}{{{\text{kA}}}}$$ is known as
Discuss
Answer & Solution
Answer: Option B
Solution:
The rate of heat flow through a body is $${\text{Q}} = \frac{{{\text{kA}}\left( {{{\text{T}}_1} - {{\text{T}}_2}} \right)}}{{\text{x}}}.$$    The term $$\frac{{\text{x}}}{{{\text{kA}}}}$$ is known as Thermal resistance.
33
Depending on the radiating properties, a body will be white when
(Where a = absorptivity, p = reflectivity, x = transmissivity)
Discuss
Answer & Solution
Answer: Option B
Solution:
Depending on the radiating properties, a body will be white when p = 1, T = 0 and a = 0
(Where a = absorptivity, p = reflectivity, x = transmissivity)
34
Depending on the radiating properties, body will be transparent when
(Where a = absorptivity, p = reflectivity, x = transmissivity)
Discuss
Answer & Solution
Answer: Option C
Solution:
Depending on the radiating properties, body will be transparent when
p = 0, x = 1 and a = 0
(Where a = absorptivity, p = reflectivity, x = transmissivity)
35
The expression Q = ρ AT4 is called
Discuss
Answer & Solution
Answer: Option B
Solution:
Stefan-Boltzmann law, statement that the total radiant heat power emitted from a surface is proportional to the fourth power of its absolute temperature. The expression Q = ρ AT4 is called Stefan-Boltzmann equation
36
In heat transfer, conductance equals conductivity (kcal/hr/sq.m/°C/cm) divided by
Discuss
Answer & Solution
Answer: Option D
Solution:
In heat transfer, conductance equals conductivity (kcal/hr/sq.m/°C/cm) divided by K.cal (heat)
37
The time constant of a thermocouple is
Discuss
Answer & Solution
Answer: Option C
Solution:
The Time Constant of a thermocouple is defined as the time required for the sensor to respond to 63.2% of its total output signal when subjected to a step change in temperature.
38
The total emissivity power is defined as the total amount of radiation emitted by a black body per unit
Discuss
Answer & Solution
Answer: Option C
Solution:
Total emissive power refers to the total amount of thermal radiation emitted by a surface (typically a black body) across all wavelengths per unit time and per unit area.

This concept is governed by Stefan-Boltzmann law, which states:

E = σT⁴

Where:
E = Total emissive power
σ = Stefan-Boltzmann constant
T = Absolute temperature of the black body

As per the definition, the total emissive power is expressed in units of watts per square meter (W/m²), indicating that it is radiation emitted per unit area.

Therefore, the correct answer is: Area (Option C).
39
Heat transfer takes place as per
Discuss
Answer & Solution
Answer: Option C
Solution:
Heat transfer takes place as per Second law of the thermodynamics it states that Heat transfer occurs spontaneously from higher- to lower-temperature bodies but never spontaneously in the reverse direction. The law states that it is impossible for any process to have as its sole result heat transfer from a cooler to a hotter object.
40
Thermal diffusivity is
Discuss
Answer & Solution
Answer: Option D
Solution:
Thermal Diffusivity is defined as the ratio of heat conducted to the heat energy stored per unit volume of a material.
Its SI unit is m2/s.
It describes how fast heat can be transferred across the medium.
Greater the value of thermal diffusivity, faster is the propagation of heat through the medium.