The ratio of thermal & electrical conductivity is same for all the metals at the same temperature; and at around room temperature, this ratio is proportional to(where, T = absolute temperature, °K) ?

Related Mcqs:

1. A furnace is made of a refractory brick wall of thickness 0.5 metre and thermal conductivity 0.7 W/m.°K For the same temperature drop and heat loss, this refractory wall can be replaced by a layer of diatomaceous earth of thermal conductivity 0.14 W/m.K and thickness ______________ metre?

   A. 0.01
   B. 0.1
   C. 0.25
   D. 0.5

2. Velocity of a gas in sound is not proportional to (where, T = Absolute temperature of the gas. P = Absolute pressure of the gas. y = Ratio of specific heats (Cp/Cv) ρ = specific weight of the gas) ?

   A. √T
   B. 1/√P
   C. √y
   D. 1/√ρ

3. Thermal diffusivity of a substance is proportional to (where, k = Thermal conductivity) ____________________?

   A. 1/k
   B. k
   C. k2
   D. 1/k2

4. One face of a furnace wall is at 1030°C and the other face is exposed to room temperature (30°C). If the thermal conductivity of furnace wall is 3 W. m-1. k-1 and the wall thickness is 0.3 m, the maximum heat loss (in W/m) is____________________?

   A. 100
   B. 900
   C. 9000
   D. 10000

5. Which of the following metals cannot be hot worked at room temperature ?

   A. Zinc
   B. Nickel
   C. Lead
   D. Tin

6. With increase in temperature, the electrical conductivity of a _________________ decreases ?

   A. Semi-conductor
   B. Metal or alloy
   C. Dielectric
   D. None of these

7. Temperature of hot gases flowing in a pipe is measured by a thermocouple inserted in the thermal well. The thermal well made of ______________ will facilitate the most accurate measurement of the temperature ?

   A. Copper
   B. Steel
   C. Aluminium
   D. Brass

8. Change in volume of metals from absolute zero temperature to their melting points is___________________?

   A. Almost same for all metals
   B. Different for different metals
   C. Less for low melting point metals
   D. Less for high melting point metals

9. Heating the Hypo-eutectoid steels to 30°C above the upper critical temperature line, soaking at that temperature and then cooling slowly to the room temperature to form a pearlite & ferrite structure is called_______________________?

   A. Tempering
   B. Hardening
   C. Annealing
   D. Normalising

10. The kinematic viscosity (in stoke) and the absolute/dynamic viscosity (in poise) are the same for ______________ at room temperature ?

    A. Air
    B. Water
    C. Mercury
    D. Alcohol