# In radioactive heat transfer, a gray surface is one

1.  Which appears gray to the eye

2.  Whose emissivity is independent of wavelength?

3.  Which has reflectivity equal to zero?

4.  Which appears equally bright from all directions?

4

Whose emissivity is independent of wavelength?

Explanation :
No Explanation available for this question

# The temperature variation under steady heat conduction across a composite slab of two materials with thermal conductivities k1 and k2 is shown in figure then, which one of the following statements holds

1.  k1 > k2

2.  k1 = k2

3.  k1 = 0

4.  k1 < k2

4

k1 < k2

Explanation :
No Explanation available for this question

# The temperature drop through the two layer furnace wall shown above is maintained at 5500C. Each layer is of equal thickness. Which for the following actions will result in lowering the temperature at the interface between the two layers

1.  Increasing the thermal conductivity of the outer layer

2.  Increasing the thermal conductivity of the inner layer

3.  Increasing the thickness of the outer layer

4.  Reducing the thickness of the inner layer

4

Increasing the thermal conductivity of the outer layer

Explanation :
No Explanation available for this question

# What happens when the thickness of insulation on a pipe exceeds the critical value

1.  Heat transfer rate increases

2.  Heat transfer rate decreases

3.  Heat transfer rate remains constant

4.  None of these

4

Heat transfer rate decreases

Explanation :
No Explanation available for this question

# In M, L, T, θ system the dimension of energy conversion factor is

1.  T-1

2.  θ-1

3.  MLTθ

4.  None of these

4

θ-1

Explanation :
No Explanation available for this question

# A composite member shown in the figure was formed at 200C and was made of two different materials P and Q. If the coefficient of thermal expansion of P is more than that Q and the composite member is heated to 1000C, then

1.  P will be in tension and Q in compression

2.  Both P and Q will be in compression

3.  P will be in compression and Q in tension

4.  Both P and Q will be in tension

4

P will be in compression and Q in tension

Explanation :
No Explanation available for this question

# Critical thickness of insulation for spheres is given by

1.  k/h

2.  k/4πh

3.  h/2k

4.  2k/h

4

2k/h

Explanation :
No Explanation available for this question

# A rectangular slab has a surface area of 1 m2 and is 4 cm thick. It transmits 10 cal/sec cm2 due to a temperature difference between its end faces. If the coefficient of thermal conductivity is 0.8 cal/sec 0C cm and the cooler end is at room temperature (200C), what is the temperature of the other face

1.  300C

2.  500C

3.  600C

4.  700C

4

700C

Explanation :
No Explanation available for this question

# Which of the following temperature measuring device will have least accuracy

1.  Clinical thermometer

2.  Alcohol filled thermometer

3.  Optical pyrometers

4.   Nitrogen filled thermometer

4

Clinical thermometer

Explanation :
No Explanation available for this question

1.  Conduction

2.  Convection

4.  All of these

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