STEADY STATE HEAT CONDUCTION MULTIPLE CHOICE QUESTIONS (MCQ) WITH ANSWERS

STEADY STATE HEAT CONDUCTION

MULTIPLE CHOICE QUESTIONS

(MCQ) WITH ANSWERS 

MCQ on steady state heat conduction

help to understand concepts in a better

manner. Steady state heat Conduction

takes place in solids by physical contact.

Conduction is invisible mode of heat

transfer. It depends on temperature

difference. Larger is the temperature

difference, greater is the rate of heat

transfer.

Fig. Conduction through a single Plain Wall (linear Temperature Variation)

Fig. Conduction through a composite wall (Linear Temperature Variation)

 

Fig. Conduction through a Cylinder (Logarithmic Temperature Variation)

_{Fig. Conduction through a Sphere (}Hyperbolic Temperature Variation)

Fig. Critical Radius of insulation, For a cylinder r_c = k/h_o and for a sphere, r_c=2k/h₀

1. During steady state heat conduction, there is a physical motion of the

(a) Crystal lattice

(b) Main body

(c) Crystal lattice as well as main body

(d) None

ANS: (a)

2. Steady state heat conduction takes place in

(a) Solids only

(b)  Liquids only

(c)  Gases only

(d) None

ANS: (a)

3. Critical thickness insulation stands for

(a) Minimum rate of heat transfer

(b) Maximum rate of heat transfer

(c) Minimum as well as maximum rate of heat transfer

(d) None

ANS: (b)

4. Biot number is the ratio of

(a) External thermal resistance to internal thermal resistance

( b) Internal thermal resistance to external thermal resistance

(c) Rate of conductive HT/Rate of Convective HT

(d) None

ANS: (b)

5. In steady state conduction heat transfer, there is constant

(a)  Rate of heat transfer with respect to time

(b)  Temperature with respect to time

(c)  Rate of heat transfer and constant temperature w r t time

( d) None

ANS: (c)

6. Thermal conductivity is the rate of heat transfer

(a) Per unit area per unit thickness

(b) Per unit area per unit temperature difference

(c) Per unit area per unit temperature difference and per unit wall thickness

( d), None

ANS: (c )

7. Pure metals thermal conductivity increases

(a)With the increase of temperature

(b) With the increase of pressure

(c) With the increase of both temperature and pressure

(d) None

ANS: ©

8. Heat transfer in a car radiator consists of

(a)(Conduction + convection)

(b) (Convection+ Conduction + convection)

(c) Radiation

(d) None

ANS: (c )

9. Internal heat generation is found in

(a) In a car radiator

(b) In an evaporator of a refrigerator

(c) In the condenser of an air conditioner

(d) None

ANS: (d)

10. Example of steady state conduction is in

(a) Atmosphere

(b) Hot car engine

(c) Hot cup of coffee

(d) None

ANS: (d)

11. Variation of temperature in steady state heat conduction through a wall is

(a) Non linear

(b) Linear

(c) Parabolic

(d) None

ANS: (b)

12. Temperature variation in Newtonian heating of a solid is

(a) Exponential

(b), Linear

(c) Parabolic

(d) None

ANS: (a)

13. Unit of temperature used in steady state heat conduction and convection is

(a) Degree centigrade

(b) Kelvin

(c) Both degree centigrade and Kelvin

(d) None

ANS: (a)

14. Range of thermal conductivity of pure metals is

1. Firstly 10 to 200

2. Secondly 10 to 300

3. Thirdly 10 to 400

4. None

ANS: (c )

15. Range of thermal conductivity for insulating & building material is

1. Firstly 023 to 5.9

2. Secondly 023 to 3.9

3. Thirdly 023 to 2.9

4. None

ANS: (c )

16. Range of thermal conductivities for liquids is

1. 1 to 1.0

2. 2 to 0.6

3. 6 to 1.6

4. None

ANS: (b)

17. Range of thermal conductivities for gases and vapors

1. Firstly 006 to 0.1

2. Secondly 006 to 0.01

3. Thirdly 006 to 0.023

4. None

ANS: (c )

18. Thermal conductivity ‘k’, electrical conductivity ‘σ’ & absolute temperature ‘T’, the ratio k/σ T is

1. Firstly 45 x 10⁺⁸

2. Secondly 45 x 10 ^-8

3. Thirdly 45 x 10^{-8 to +8}

4. None

ANS: (b)

19. The ratio of thermal conductivities of good conductors and good insulators is

1. Firstly 10²

2. Secondly 10³

3. Thirdly 10⁴

4. None

ANS: (c )

20. The ratio of electrical conductivity of good conductors and good insulators is

1. Firstly 10⁴

2. Secondly 10¹⁴

3. Thirdly 10²⁴

4. None

ANS: (c )

24. Unit of thermal resistance is

• (a)W/m ^o C

•  (b) W/m^{2 o} C

• (c) W/K

•  (d) None

• ANS: (a)

Q.25 Critical radius of insulation refers to

(a) Minimum rate of heat transfer

(b) Maximum rate of heat transfer

(c) Constant rate of heat transfer

(d) None

(Ans: b)

26. Critical radius of insulation for a cylinder is equal to

(a) 3k/h_o

(b) 2k/h_o

(c) 1k/h_o

(d) None

(Ans: c)

27. Critical radius of insulation for a sphere is equal to

(a) 3k/h

(b) 2k/ho

(c) 1k/ho

(d) None

(Ans: b)

28. Critical radius of insulation for a plane wall is equal to

(a) 3k/h

(b) 2k/ho

(c) 1k/ho

(d) None

(Ans: d)

29. Thermal conductive resistance of a plane wall in steady state heat conduction is

(a) x/kA

(b) xL/kA

(c) h L/k

(d) None

(Ans: a)

30. Thermal convective resistance is

(a) x/kA

(b) 1/hA

 (c) hL/k

(d) None

(Ans:b)

31. Thermal resistance of combined conduction and convection is

(a) U/kA

(b) L/UA

(c) 1/UA

(d) None 

(Ans: c)

32. Increase in thermal diffusivity stands for

(a) Faster heat diffusion

(b) Slower heat diffusion

(c) Constant heat diffusion

(d) None

(ANS: a)

33. Biot number deals with

(a) Steady state heat conduction

(b) Unsteady state heat conduction

(c) constant rate of heat conduction

(d) None

(Ans: b)

34. Biot number

(a) Varies with time

(b) Varies directly with k

(c) Varies inversely with k

(d) None

(Ans: c)

35. Conductive resistance in a pipe of single wall is

(a) ln(r_o/r_i )/2π kL

(b) ln(r_o/r_i )/π kL

(c) ln(r_o/r_i )/2πr kL

(d) None

(Ans: a )

35. Thermal resistance for a single wall hollow sphere will be 

(a) (r_o –r_i)/4πk r_ir_o

(b) (r_o –r_i)/2πk r_ir_o

(c) (r_o –r_i)/6πk r_ir_o

(d) None

(Ans: a) 

36. Variation of thermal conductivity of a non conductor with temperature is

(a) k_o(1 + β t)

(b) k_o(1 — βt)

(c) k_o(1 ± βt)

(d) None

(Ans: a) 

Q37. Poisson’ equation in steady state heat conduction deals with

(a) Steady state heat conduction
(b) Unsteady state heat conduction
(c) Steady as well as unsteady states of conduction
(d) None
(Ans: a)

38.Laplace equation in heat transfer deals with

(a) Steady state conduction heat transfer
(b) Unsteady state conduction heat transfer
(c) Steady as well as unsteady states conduction heat transfer
(d) None
(Ans: a)

39. Poisson’ equation in heat transfer deals with

(a) Internal heat generation
(b) External heat generation
(c) Internal as well as external heat generation
(d) None
(Ans: a)

40. Laplace equation in heat transfer deals with

(a) Internal heat generation
(b) External heat generation
(c) Internal as well as external heat generation
(d) None
(Ans: d)

41. Rectangular coordinates used in heat transfer are

(a) r, θ, φ
(b) r, θ, z
(c) x, y, z
(d) None
(Ans:c)

42. Cylindrical coordinates used in heat transfer are

(a) r, θ, φ
(b) r, θ, z
(c) x, y, z
(d) None
(Ans: b)

43. Spherical coordinates used in heat transfer are

(a) r, θ, φ
(b) r, θ, z
(c) x, y, z
(d) None
(Ans: a)

44. Size of the element in rectangular coordinates in the derivation of 3-D conduction equation is

(a) r dθ, dr, dz
(b) dx, dy, dz
(c) r dθ, dr, r sinθ dφ
(d) None
(Ans: b)

45. Size of the element in spherical coordinates in the derivation of 3-D steady state heat conduction equation is

(e) r dθ, dr, dz
(f) dx, dy, dz
(g) r dθ, dr, r sinθ dφ
(h) None
(Ans: c)

46. Size of the element in cylindrical coordinates in the derivation of 3-D conduction equation is

(i) r dθ, dr, dz
(j) dx, dy, dz
(k) r dθ, dr, r sinθ dφ
(l) None
(Ans: a)

47. Poisson’ equation in conduction heat transfer deals with

(a) Steady state conduction heat transfer
(b) Unsteady state conduction heat transfer
(c) Steady as well as unsteady states conduction heat transfer
(d) None
(Ans: a)

48. Laplace equation in heat transfer deals with

(a) Steady state conduction heat transfer
(b) Unsteady state conduction heat transfer
(c) Steady as well as unsteady states of conduction heat transfer
(d) None
(Ans: a)

49. Poisson’ equation in steady state heat conduction deals with

(a) Internal heat generation
(b) External heat generation
(c) Internal as well as external heat generation
(d) None
(Ans: a)

50. Laplace equation in steady state heat conduction deals with

(a) Internal heat generation
(b) External heat generation
(c) Internal as well as external heat generation
(d) None
(Ans: d)

51. Rectangular coordinates used in steady state heat conduction are

(a) r, θ, φ
(b) r, θ, z
(c) x, y, z
(d) None
(Ans: c)

52. Cylindrical coordinates used in conduction heat transfer are

(a) r, θ, φ
(b) r, θ, z
(c) x, y, z
(d) None
(Ans: b)

53. Spherical coordinates used in conduction heat transfer are

(a) r, θ, φ
(b) r, θ, z
(c) x, y, z
(d) None
(Ans: a)

54. Size of the element in rectangular coordinates in the derivation of 3-D conduction equation is

(a) r dθ, dr, dz
(b) dx, dy, dz
(c) r dθ, dr, r sinθ dφ
(d) None
(Ans: b)

55. Size of the element in spherical coordinates in the derivation of 3-D conduction equation is

(e) r dθ, dr, dz
(f) dx, dy, dz
(g) r dθ, dr, r sinθ dφ
(h) None
(Ans: c)

56. Size of the element in cylindrical coordinates in the derivation of 3-D conduction equation is

(i) r dθ, dr, dz
(j) dx, dy, dz
(k) r dθ, dr, r sinθ dφ
(l) None
(Ans: a)

57. Conduction with internal heat generation is found in a

• 1. Pressure cooker

  2. Indane gas cylinder

  3. Geyser

  4. None

ANS: (c )

    58. Conduction with internal heat generation is found in a

• 1. Washing clothes with hot water

  2. Making rice on gas

  3. Boiling of potatoes

  4. None

ANS: (d)

    59. Conduction with internal heat generation is found in a

• 1. Physical reaction

  2. Chemical reaction

  3. Physical & chemical reaction

  4. None

ANS: (b)

    60. Conduction with internal heat generation is found in a

• 1. Nuclear reactor

  2. Radiation shield

  3. Umbrella

  4. None

ANS: (a)

    61. The following is the case of internal heat generation

• 1. Conversion of pressure energy into kinetic energy

  2. Change of kinetic energy into potential energy

  3. Conversion of electrical energy into thermal energy

  4. None

ANS: (c )

    62. The equation for steady state heat conduction with internal heat generation is

• 1.  when d²t/dx² –q_g/k=0

  2. if   d²t/dx² + q_g/k=0

  3. d²t/dx² q_g/k=0

  4. None

ANS: (b)

    63. Case of a plane wall with uniform heat generation is

• 1. Unsteady state conduction

  2. Steady state conduction

  3. Steady & unsteady state conduction

  4. None

ANS: (b)

    64. Case of a plane wall with uniform heat generation is

• 1. One dimensional heat conduction

  2. 2-dimensional heat conduction

  3. 3-dimensional heat conduction

  4. None

ANS: (a)

    65. Temperature variation in a plane wall with uniform heat generation is

• 1. Linear

  2. Parabolic

  3. Curvilinear

  4. None

ANS: (b)

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