For a given heat flow and for the same thickness, the temperature drop across the material will be maximum for

Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow, and k = Thermal conductivity of the body)

A

k. A. (dT/dx)

B

k. A. (dx/dT)

C

k. (dT/dx)

D

k. (dx/dT)

Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow and k = Thermal conductivity of the body)

A

$${\text{kA}}\frac{{{\text{dT}}}}{{{\text{dx}}}}$$

B

$${\text{kA}}\frac{{{\text{dx}}}}{{{\text{dT}}}}$$

C

$${\text{k}}\frac{{{\text{dT}}}}{{{\text{dx}}}}$$

D

$${\text{k}}\frac{{{\text{dx}}}}{{{\text{dT}}}}$$

For a given heat flow and for the same thickness, the temperature drop across the material will be maximum for ____________

A

copper

B

steel

C

glass-wool

D

refractory brick

Thickness of 8 tyres L, M, N, O, P, Q, R and S is compared. Thickness of no two tyres is same. Thickness of N is more than L but less than 6 tyres. Thickness of O is more than M but less than Q. Thickness of P is less than only two tyres. Thickness of Q is not more than P. Which of the following statement is not correct?

A

If thickness of P is 108 cm, then sum of thickness of R and S can be 219 cm

B

Thickness of R is less than S

C

Thickness of O is less than P

D

L < N < M < O < Q < P < S < R can be the correct sequence of their thickness

The following data pertains to a hollow cylinder and a hollow sphere made of same material and having the same temperature drop over the wall thickness Inside radius = 0.1 m and outside surface area = 1 square meter If the outside radius for both the geometrics is same, calculate the ratio of heat flow in the cylinder to that of sphere?

A

0.056

B

2.345

C

1.756

D

3.543

Applying a pressure drop across a capillary results in a volumetric flow rate 'Q' under laminar flow conditions. The flow rate for the same pressure drop, in a capillary of the same length but half the radius is

A

$$\frac{{\text{Q}}}{2}$$

B

$$\frac{{\text{Q}}}{4}$$

C

$$\frac{{\text{Q}}}{8}$$

D

$$\frac{{\text{Q}}}{{16}}$$

A composite wall consists of two plates A and B placed in series normal to the flow of heat. The thermal conductivities are kA and kB and the specific heat capacities are CPA and CPB for plates A and B respectively. Plate B has twice the thickness of plate A. At steady state, the temperature difference across plate A is greater than that across plate B, when

A

CPA > CPB

B

CPA PB

C

KA B

D

KA>2 kB

A composite wall consists of two plates A and B placed in series normal to the flow of heat. The thermal conductivities are k_A and k_B and the specific heat capacities are C_PA and C_PB for plates A and B respectively. Plate B has twice the thickness of plate A. At steady state, the temperature difference across plate A is greater than that across plate B, when

A

C_PA > C_PB

B

C_PA PB

C

k_A B

D

k_A > 2 k_B

A composite flat wall of a furnace is made of two materials 'A' and 'B'. The thermal conductivity of 'A' is twice of that of material 'B', while the thickness of layer of 'A' is half that of B. If the temperature at the two sides of the wall are 400 and 1200°K, then the temperature drop (in °K) across the layer of material 'A' is

A

125

B

133

C

150

D

160

Out of the following, maximum temperature drop for a given heat flow & for the same thickness will be in the case of

A

Steel

B

Glass wood

C

Copper

D

Fireclay bricks

For a given heat flow and for the same thickness, the temperature drop across the material will be maximum for

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