Fourier Equation And Thermal Conductivity(Heat Transfer ) Questions and answers for exam Preparation

Question 1. The famous Fourier series is named after

Diller and Ryan
J.B. Joseph Fourier
Stefan- Boltzmann
Wein’s

Explanation:-

Answer: Option B. -> J.B. Joseph Fourier
Answer: (b).J.B. Joseph Fourier

Question 2. Fourier law of heat conduction is best represented by

Q = -k A d t /d x
Q = k A d x/d t
Q = -k A
Q = k d t/d x

Explanation:-

Answer: Option A. -> Q = -k A d t /d x
Answer: (a).Q = -k A d t /d x

Question 3. Negative sign in Fourier heat conduction equation indicates

Heat always flow is in the direction of positive temperature gradient
Heat always flow in the direction of negative temperature gradient
No heat flow is there
Data is insufficient

Explanation:-

Answer: Option B. -> Heat always flow in the direction of negative temperature gradient
Answer: (b).Heat always flow in the direction of negative temperature gradient

Question 4. Consider the following statements:
The Fourier heat conduction equation
Q = -k A d t /d x
Presumes
i) Steady state conditions
ii) Constant value of thermal conductivity
iii) Uniform temperature at the wall surface
iv) One dimensional heat flow
Which of these statements are correct?

1, 2 and 3
1, 2 and 4
2, 3 and 4
1, 3 and 4

Explanation:-

Answer: Option D. -> 1, 3 and 4
Answer: (d).1, 3 and 4

Question 5. Here are some assumptions that are made for Fourier law. Identify the wrong one

No internal heat generation
Steady state heat conduction
Non- linear temperature profile
Isotropic and homogenous material

Explanation:-

Answer: Option C. -> Non- linear temperature profile
Answer: (c).Non- linear temperature profile

Question 6. The diagram shows heat conduction through a plane wall. The surface temperature is 475 K and it radiates heat to the surroundings at 335 K. If thermal conductivity of the material is 12.5 W/m degree, find the temperature gradient. Let convective coefficient be 80 W/m² degree and radiation factor is 0.9

– 1052.4 degree celsius
– 2052.4 degree celsius
– 3052.4 degree celsius
– 4052.4 degree celsius

Explanation:-

Answer: Option A. -> – 1052.4 degree celsius
Answer: (a).– 1052.4 degree celsius

Question 7. From the concept of kinetic theory, mean travel velocity of the gas molecules is prescribed by the relation
(Where,
G = Universal gas constant
M = Molecular weight of the gas
T = Absolute temperature)

V = (3M/GT)⅟₂
V = (3GT/M)⅟₂
V = (6T/GM)⅟₂
V = (3GT/2M)⅟₂

Explanation:-

Answer: Option B. -> V = (3GT/M)⅟₂
Answer: (b).V = (3GT/M)⅟₂

Question 8. The value of Lorenz number in 10¯⁸ W ohms/K² is

2.02
2.35
2.56
2.45

Explanation:-

Answer: Option D. -> 2.45
Answer: (d).2.45

Question 9. Low temperature insulation are used when the enclosure is at a temperature lower than the ambient temperature. Which one of the following is not a low temperature insulation?

Asbestos
Cork
Cattle hair
Slag wool

Explanation:-

Answer: Option A. -> Asbestos
Answer: (a).Asbestos

Question 10. Consider the following parameters
(i) Composition
(ii) Density
(iii) Porosity
(iv) Structure
Then, thermal conductivity of glass wool varies from sample to sample because of variation is

1 and 2
1, 2, 3 and 4
1 and 3
1, 2 and 3

Explanation:-

Answer: Option B. -> 1, 2, 3 and 4
Answer: (b).1, 2, 3 and 4