In SI units, thermal conductivity is expressed in__________________?

Related Mcqs:

1. The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K0 + at, where, K is the thermal conductivity and T is the temperature (in °K). The units of ‘a’ in SI system will be________________?

   A. W/m.k
   B. W/m
   C. W/m.k2
   D. None, ‘a’ is just a number

2. For gases, the thermal conductivity increases with temperature rise. For liquids, with increase in concentration, its thermal conductivity generally ?

   A. Decreases
   B. Increases
   C. Remains unchanged
   D. Increases exponentially

3. Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)?

   A. x/KA
   B. KA/x
   C. K/Ax
   D. A/Kx

4. With increase in temperature, the thermal conductivity of most liquids_________________?

   A. Increases
   B. Decreases
   C. Remain same
   D. First increases upto a certain temperature and then becomes constant

5. Which of the following has maximum thermal conductivity ?

   A. Iron
   B. Coal
   C. Nitrogen
   D. Tar

6. Three materials A, B and C of equal thickness and of thermal conductivity of 20, 40 & 60 kcal/hr. m. °C respectively are joined together. The temperature outside of A and C are 30°C and 100°C respectively. The interface between B and C will be at a temperature of ____________ °C?

   A. 40
   B. 95
   C. 70
   D. 50

7. The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m2.K. At steady state, the temperature of the right face in °C is____________________?

   A. 77.2
   B. 71.2
   C. 63.8
   D. 48.7

8. 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

9. Low thermal conductivity of heat insulating materials is due to its_______________?

   A. Dense structure
   B. High proportion of air space
   C. High specific heat
   D. None of these

10. Thermal conductivity of a conducting solid material depends upon its_______________?

    A. Temperature
    B. Porosity
    C. Both A. & B.
    D. Neither A. nor B.