Planck’s distribution law is valid for _____________ bodies?

Related Mcqs:

1. If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows _____________ law?

   A. Parabolic
   B. Hyperbolic
   C. Linear
   D. Logarithmic

2. “The ratio of the total emissive power to the absorptivity for all bodies is same at ther-mal equilibrium”. This is ______________ law?

   A. Kirchoff’s
   B. Planck’s
   C. Wien’s displacement
   D. Stefan-Boltzmann

3. If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows ____________ law?

   A. Hyperbolic
   B. Parabolic
   C. Linear
   D. Logarithmic

4. Dittus-Boelter equation used for the determination of heat transfer co-efficient is valid ___________________?

   A. For fluids in laminar flow
   B. For fluids in turbulent flow
   C. When Grashoff number is very important
   D. For liquid metals

5. The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter D. as _________________?

   A. D-1.8
   B. D-0.2
   C. D0.2
   D. D1.8

6. Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8. Pr n, is not valid, if the value of __________________?

   A. n = 0.4 is used for heating
   B. n = 0.3 is used for cooling
   C. Reynolds number for the flow involved is > 10000
   D. Reynolds number for the flow involved is < 2100

7. For what value of Prandtl number, the Col-burn analogy is valid ?

   A. 0.06 to 120
   B. 0.6 to 120
   C. 1 to 103
   D. 1 to 50

8. Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by h = 0.023 (K/D) (DVρ/μ)0.8 (CP.μ/k)0.4. This is valid for the value of NRe equal to_______________?

   A. 4000
   D. > 10000

9. Stefan’s block body radiation law can also be derived from ______________ law?

   A. Kirchoff’s
   B. Planck’s
   C. Fourier’s
   D. None of these

10. Heat transfer by radiation between two bodies at T1 & T2 and in an ambient temperature of Ta°C depends on_____________?

    A. T1 – T2
    B. T1 – Ta
    C. T2 – Ta
    D. None of these