# HMT Practice Questions

Q1) Thermal conductivity of a given material

a)  Can depend on temperature

b) Can be different through different directions of material

c) Both (a) and (b)

d) Only (a)

Q2) There is a metal rod 10 m length at room temperature, suddenly over the two axial ends of the rod, constant temperature heat sources are applied with temperatures 400K and 300K respectively so that heat can transfer from hot to cold source through rod. The time required for rod up to which the heat transfer though it will be most closer to steady state will be.

a) 10.5 hours

b) 35.1 hours

c) 12    hours

d) 22.2 hours

Q3) For getting the advantage of  insulation over a cylindrical body, the thickness of insulation must be.

a) Just more than critical thickness of insulation

b) Less than critical thickness of insulation

c) Less than the thickness where the thermal resistance is equal to no insulation

d) More than the thickness where the thermal resistance is equal to no insulation

Q4) The unit of thermal resistance is

a) °C/W

b) °C/mW

c)  W/°C

d) K/W  (K-Kelvin)

Q5) Which of the following modes of heat transfer depends on temperature difference

a) Conduction

b) Conduction and convection

d) None of these

Q6)  In winters and same surroundings applied, an iron chair will be

a) hotter than a wooden chair

b) cooler than a wooden chair

c) at same temperature to that of wooden chair

d) None of these

Q7) For thermal conductivity (K), convective heat transfer coefficient (h), thermal resistance (R) and thermal diffusivity α, which statement is correct

a) All are properties of a substance

b) Only K and R are properties

c) Only K and α are properties

d) Only h and K are properties

Q8) Out the following, the most general form of heat conduction equation will be Q9) Heat is transferring steadily from a metal rod whose thermal conductivity is 111W/mK. In case, The temperature difference across the two ends are 40°C and 10°C and length is 4m. In case the diameter of rod is 1 cm, the heat transfer rate will be.

a) 0.065W

b) 0.76 W

c) 0.65W

d) None

Q10) Two Slabs of different materials are placed one over another and the Thermal resistance of the two are mentioned in the diagram. The heat is transferring in vertically upward direction. The net thermal resistance will be,

a) 30 units

b) 6.66 units

c) Less than 30 units

d) More that 30 units.