Conduction - Mechanical Engineering (MCQ) questions and answers

1)   How does the thermal conductivity of a material change with respect to change in temperature of the same material?

a. thermal conductivity of a material increases with increase in its temperature
b. thermal conductivity of a material decreases with increase in its temperature
c. thermal conductivity of a material remains same with change in its temperature
d. unpredictable
Answer  Explanation 

ANSWER: thermal conductivity of a material increases with increase in its temperature

Explanation:
No explanation is available for this question!


2)   What is the correct formula for the temperature distribution in infinitely long fin?
Where,
m = √(hP/kA)
h = convective heat transfer coefficient
P = perimeter of the fin
k = thermal conductivity of fin
A = cross-sectional area of the fin
T = Temperature of the fin at the distance x from the base of fine
and the constants C1 and C2 depend on the boundary conditions
Ts = Base temperature of the fin
T = Temperature of surrounding fluid


a. (Ts – T) / (T – T) = C2emx
b. (Ts – T) / (T – T) = C2e– mx
c. (T – T) / (Ts – T) = C2emx
d. (T – T) / (Ts – T) = C2e– mx
Answer  Explanation 

ANSWER: (T – T) / (Ts – T) = C2e– mx

Explanation:
No explanation is available for this question!


3)   Heat transfer deals with the rate of

a. work transfer
b. temperature transfer
c. energy transfer
d. none of the above
Answer  Explanation 

ANSWER: energy transfer

Explanation:
No explanation is available for this question!


4)   If the body or element does not produce heat, then the general heat conduction equation which gives the temperature distribution and conduction heat flow in an isotropic solid reduces to(∂T/∂x2) + (∂T/∂y2) + (∂T/∂z2) = (1/α)(∂T/∂t)this equation is known as

a. Laplace equation
b. Fourier equation
c. Poisson equation
d. none of the above
Answer  Explanation 

ANSWER: Fourier equation

Explanation:
No explanation is available for this question!


5)   For effective working of fins, the thickness of the fines should be

a. large
b. small
c. thickness of fin does not affect the fin effectiveness
d. unpredictable
Answer  Explanation 

ANSWER: small

Explanation:
No explanation is available for this question!


6)   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 

ANSWER: because heat is transferred from higher temperature to lower temperature

Explanation:
No explanation is available for this question!


7)   The cooling of a metal ball of volume V, in large quantity of fluid is analogous to

a. discharging of battery in an electric system
b. discharging of capacitor in an electric system
c. generation of heat in resistor in an electrical system
d. none of the above
Answer  Explanation 

ANSWER: discharging of capacitor in an electric system

Explanation:
No explanation is available for this question!


8)   What should be the Biot number to assume the body at uniform temperature?

a. the Biot number should be less than 0.1
b. the Biot number should be more than 0.1
c. the Biot number should be equal to 0.1
d. none of the above
Answer  Explanation 

ANSWER: the Biot number should be less than 0.1

Explanation:
No explanation is available for this question!


9)   What is the correct formula for The Biot number?

a. hl/k
b. k/hl
c. l/hk
d. hk/l
Answer  Explanation 

ANSWER: hl/k

Explanation:
No explanation is available for this question!


10)   The Biot number or Biot modulus is given by

a. the ratio of external convection resistance to the internal conduction resistance
b. the ratio of internal conduction resistance to the external convection resistance
c. multiplying internal conduction resistance and external convection resistance
d. none of the above
Answer  Explanation 

ANSWER: the ratio of internal conduction resistance to the external convection resistance

Explanation:
No explanation is available for this question!


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