A. Iron
B. Coal
C. Nitrogen
D. Tar
Related Mcqs:
- 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 - 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 - Which of the following has the minimum thermal conductivity ?
A. Nitrogen
B. Steel
C. Carbon black
D. Tar - Which of the following has the highest thermal conductivity ?
A. Brick
B. Air
C. Water
D. Silver - With increase in temperature, the thermal conductivity of fresh lubricating oil ___________________?
A. Increases
B. Decreases
C. Remains unchanged
D. May increase or decrease; depends on its composition - What is the unit of thermal conductivity ?
A. Kcal/hr. m2 °C
B. Kcal/hr.m.°C
C. Kcal/hr.m
D. Kcal/hr. °C - 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 - 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 - The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) ?
A. K/h0
B. 2K/h0
C. h0/K
D. h0/2K - What is the thermal conductivity of a perfect heat insulator ?
A. Zero
B. One
C. ∞
D. Between 0 and ∞
