# Heat Transfer Test Questions Set - 2

1)   The conduction heat transfer with combination of transfer of material also is called as

a. material conduction heat transfer
b. convection heat transfer
c. solid convection heat transfer
d. none of the above
 Answer  Explanation  Related Ques ANSWER: convection heat transfer Explanation: No explanation is available for this question!

2)   According to the Fourier's law of heat conduction, the rate of heat transfer by conduction depends upon

a. area of cross section normal to the heat flow
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: both a. and b. Explanation: No explanation is available for this question!

3)   What is the temperature gradient in the conduction heat transfer?

a. change in temperature per unit change in time
b. change in temperature per unit change in distance in the direction of heat flow
c. change in temperature per unit change in cross-sectional area normal to the direction of heat flow
d. change in temperature per unit change in cross-sectional area parallel to the direction of heat flow
 Answer  Explanation  Related Ques ANSWER: change in temperature per unit change in distance in the direction of heat flow Explanation: No explanation is available for this question!

4)   Why is the negative sign introduced in the equation of Fourier's law of heat conduction?

q = – kA (dT / dx)

a. because heat transfer rate is inversely proportional to temperature gradient
b. because value of thermal conductivity k is negative
c. because heat is transferred from higher temperature to lower temperature
d. none of the above
 Answer  Explanation  Related Ques ANSWER: because heat is transferred from higher temperature to lower temperature Explanation: No explanation is available for this question!

5)   The value of thermal conductivity k depends upon

a. the material through which the heat is transferred
b. the intensity of heat energy which is being transferred
c. the area which is parallel to the heat transfer
d. all of the above
 Answer  Explanation  Related Ques ANSWER: the material through which the heat is transferred Explanation: No explanation is available for this question!

6)   The materials which have low thermal conductivity are called as ____________

a. thermal conductors
b. thermal resistors
c. thermal insulators
d. none of the above
 Answer  Explanation  Related Ques ANSWER: thermal insulators Explanation: No explanation is available for this question!

7)   How does the radiation heat transfer occur through perfect vacuum?

a. by light waves
b. by electromagnetic waves
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: both a. and b. Explanation: No explanation is available for this question!

8)   The Stefan-Boltzmann law of thermal radiation is applicable for

a. white body
b. gray body
c. black body
d. all of the above
 Answer  Explanation  Related Ques ANSWER: black body Explanation: No explanation is available for this question!

9)   According to the Stefan-Boltzmann law of thermal radiation for a perfect radiator, the rate of radiant energy per unit area is proportional to

a. the temperature of that radiator
b. the square of the temperature of that radiator
c. the cube of the temperature of that radiator
d. the fourth power of the temperature of that radiator
 Answer  Explanation  Related Ques ANSWER: the fourth power of the temperature of that radiator Explanation: No explanation is available for this question!

10)   In the equation for the rate radiant heat energy from a perfect radiator q = σ A T4 the constant σ is called as

a. Black body constant
c. Stefan-Boltzmann constant
d. none of the above
 Answer  Explanation  Related Ques ANSWER: Stefan-Boltzmann constant Explanation: No explanation is available for this question!

11)   Which of the following fluid can be considered as an ideal fluid?

a. viscous fluid
b. non-viscous fluid
c. compressible fluid
d. all of the above
 Answer  Explanation  Related Ques ANSWER: non-viscous fluid Explanation: No explanation is available for this question!

12)   Consider a fluid of height H, flowing on a stationary plate as shown in figure. The top most layer of the fluid is moving with velocity U0.
Which of the following condition is correct for the given condition? a. The shear stress (τ) is directly proportional to (H x U0)
b. The shear stress (τ) is directly proportional to (H / U0)
c. The shear stress (τ) is directly proportional to (U0 / H)
d. none of the above
 Answer  Explanation  Related Ques ANSWER: The shear stress (τ) is directly proportional to (U0 / H) Explanation: No explanation is available for this question!

13)   What is the correct formula for the shear stress (τ) in a flowing fluid according to the Newton's law of viscosity?

Where,
μ = absolute viscosity of the flowing fluid
(du / dy) = change in velocity of a layer per unit change in distance of that layer from the surface
A = area of the surface on which the fluid is flowing

a. (τ) = (1 / μ) (du / dy)
b. (τ) = μ (du / dy)
c. (τ) = μ A (du / dy)
d. none of the above
 Answer  Explanation  Related Ques ANSWER: (τ) = μ (du / dy) Explanation: No explanation is available for this question!

14)   What is the SI unit for absolute or dynamic viscosity (μ)?

a. Ns/m2
b. Nm2/s
c. N/m2s
d. N/m2
 Answer  Explanation  Related Ques ANSWER: Ns/m2 Explanation: No explanation is available for this question!

15)   What is the relation between the absolute viscosities of liquid and gas?

a.liquid) ≈ (μgas)
b.liquid) << (μgas)
c.liquid) >> (μgas)
d. none of the above
 Answer  Explanation  Related Ques ANSWER: (μliquid) >> (μgas) Explanation: No explanation is available for this question!

16)   The viscosity of a liquid

a. increases with increase in liquid temperature
b. decreases with increase in liquid temperature
c. is not affected by the change in liquid temperature
d. is unpredictable
 Answer  Explanation  Related Ques ANSWER: decreases with increase in liquid temperature Explanation: No explanation is available for this question!

17)   How is the viscosity of gas affected by change in its temperature?

a. viscosity of a gas decreases with increase in temperature of gas
b. viscosity of a gas increases with increase in temperature of gas
c. viscosity of a gas is not affected by change in temperature of gas
d. viscosity of a gas is unpredictable
 Answer  Explanation  Related Ques ANSWER: viscosity of a gas increases with increase in temperature of gas Explanation: No explanation is available for this question!

18)   What is kinematics viscosity of a fluid?

a. dynamic viscosity per unit volume of the fluid
b. dynamic viscosity per unit weight of the fluid
c. dynamic viscosity per unit density of the fluid
d. none of the above
 Answer  Explanation  Related Ques ANSWER: dynamic viscosity per unit density of the fluid Explanation: No explanation is available for this question!

19)   The heat transfer is largely governed by conduction from the surface of the fluid, when

a. the velocity of the fluid is high
b. the velocity of the fluid is small
c. the velocity of the fluid is small as well as high
d. none of the above
 Answer  Explanation  Related Ques ANSWER: the velocity of the fluid is small Explanation: No explanation is available for this question!

20)   Generally, thermal conductivity of liquids is

a. very high
b. very small
c. varies from very small to very high
d. unpredictable
 Answer  Explanation  Related Ques ANSWER: very small Explanation: No explanation is available for this question!

21)   The emissive power of a body depends upon

a. temperature of the body
b. characteristics of the surface of the body
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: both a. and b. Explanation: No explanation is available for this question!

22)   At a given temperature if wavelengths are changed, the quality of radiation per unit wavelength

a. will always be constant
b. will also be changed
c. will be changed sometimes but sometimes be constant
d. unpredictable
 Answer  Explanation  Related Ques ANSWER: will also be changed Explanation: No explanation is available for this question!

23)   What is the relation between temperature of a body and the wavelength of its emitted radiation at its maximum emissive power?

a. as temperature of a body increases the wavelength of its emitted radiation also increases at its maximum emissive power
b. as temperature of a body increases the wavelength of its emitted radiation decreases at its maximum emissive power
c. as temperature of a body increases the wavelength of its emitted radiation does not change only at its maximum emissive power
d. none of the above
 Answer  Explanation  Related Ques ANSWER: as temperature of a body increases the wavelength of its emitted radiation decreases at its maximum emissive power Explanation: No explanation is available for this question!

24)   Which of the following relation is correct for the radiation?

25)   What is the relation between reflectivity (ρ), absorptivity (α) and transmissivity (τ)?

a. ρ – α + τ = 1
b. ρ + α – τ = 1
c. ρ + α + τ = 1
d. ρ – α – τ = 1
 Answer  Explanation  Related Ques ANSWER: ρ + α + τ = 1 Explanation: No explanation is available for this question!

26)   What is the opaque body?

a. the body which does not reflect radiation
b. the body which does not absorb radiation
c. the body which does not transmit radiation
d. all of the above
 Answer  Explanation  Related Ques ANSWER: the body which does not transmit radiation Explanation: No explanation is available for this question!

27)   What is diffuse reflection of radiation?

a. the reflection of radiation on a rough surface which occurs in all directions
b. the reflection of radiation on a rough surface which occurs in a single direction
c. the reflection of radiation on a smooth surface
d. none of the above
 Answer  Explanation  Related Ques ANSWER: the reflection of radiation on a rough surface which occurs in all directions Explanation: No explanation is available for this question!

28)   The reflection in which the angle of incident is equal to the angle of reflection is called as

a. regular reflection
b. specular reflection
c. both a. and b.
d. none of the above
 Answer  Explanation  Related Ques ANSWER: both a. and b. Explanation: No explanation is available for this question!

29)   The values of reflectivity (ρ), absorptivity (α) and transmissivity (τ) of a body are depend upon

a. material of the body
b. surface condition of the body
d. all of the above
 Answer  Explanation  Related Ques ANSWER: all of the above Explanation: No explanation is available for this question!

30)   Generally, the convection heat transfer coefficient in drop-wise condensation is

a. lower than the convection heat transfer coefficient in film condensation
b. higher than the convection heat transfer coefficient in film condensation
c. equal to the convection heat transfer coefficient in film condensation
d. unpredictable
 Answer  Explanation  Related Ques ANSWER: higher than the convection heat transfer coefficient in film condensation Explanation: No explanation is available for this question!

31)   Surface coating is suitable to maintain

a. drop-wise condensation
b. film condensation
c. both drop-wise and film condensation
d. none of the above
 Answer  Explanation  Related Ques ANSWER: drop-wise condensation Explanation: No explanation is available for this question!

32)   Which theory is widely used to determine the heat transfer coefficient for film condensation on surfaces?

a. Reynold's theory
b. Grashof's theory
c. Nusselt's theory
d. Prandtl's theory
 Answer  Explanation  Related Ques ANSWER: Nusselt's theory Explanation: No explanation is available for this question!

33)   In a film condensation, the vertical plate temperature should be

a. more than the saturation temperature of the vapour (Ts)
b. less than the saturation temperature of the vapour (Ts)
c. equal to the saturation temperature of the vapour (Ts)
d. none of the above
 Answer  Explanation  Related Ques ANSWER: less than the saturation temperature of the vapour (Ts) Explanation: No explanation is available for this question!

34)   According to the Nusselt's theory, to determine the heat transfer coefficient for film condensation on surfaces,

a. the vapour should be pure, dry and saturated
b. the condensate flow should be laminar
c. heat transfer should be at steady state
d. all of the above
 Answer  Explanation  Related Ques ANSWER: all of the above Explanation: No explanation is available for this question!