Heat Transfer Mock Test 5

10%

Question 1 of 10

1. When the incident surface is a sphere, the projection of surface normal to the line of propagation is the silhouette disk of the sphere which is a circle of the diameter of

Sphere

Hyperbola

Parabola

Triangle

Question 1 of 10

Question 2 of 10

2. The observed solar constant S₀, the true solar constant S and the angular elevation Z of the sun are related by the expression

S₀ =S a ^{SEC Z}

S₀ =4 S a ^{SEC Z}

S₀ =3 S a ^{SEC Z}

S₀ =2 S a ^{SEC Z}

Question 2 of 10

Question 3 of 10

3. The value of solar constant varies between

1987 and 2346 W/m²

1345 and 1453 W/m²

1335 and 1815 W/m²

1123 and 1237 W/m²

Question 3 of 10

Question 4 of 10

4. What is the wavelength band for solar radiation?

1 * 10 ^-1 to 3 micron meter

1 * 10 ^-1 to 10 micron meter

1 * 10 ^-1 to 2 micron meter

1 * 10 ^-1 to 1 micron meter

Question 4 of 10

Question 5 of 10

5. The value of radiation coefficient or the Stefan-Boltzmann constant is

5.67 * 10^-6 W/m² K⁴

5.67 * 10^-5 W/m² K⁴

5.67 * 10^-8 W/m² K⁴

5.67 * 10^-7 W/m² K⁴

Question 5 of 10

Question 6 of 10

6. With an increase in wavelength, the monochromatic emissive power of a black body

Decreases

Increases

Decreases, reaches a minimum and then increases

Increases, reaches a maximum and then decreases

Question 6 of 10

Question 7 of 10

7. A 100 W light bulb has a tungsten filament (emissivity = 0.30) which is required to operate at 2780 K. If the bulb is completely evacuated, calculate the minimum surface area of the tungsten filament

2.98 * 10 ^-4 m²

1.98 * 10 ^-4 m²

3.98 * 10 ^-4 m²

0.98 * 10 ^-4 m²

Question 7 of 10

Question 8 of 10

8. In the given diagram let r be the length of the line of propagation between the radiating and the incident surfaces. What is the value of solid angle W?

A cos α

2A cos α

A sin α

Question 8 of 10

Question 9 of 10

9. If radiant energy E_B emitted by the black surface strikes the non-black surface. If non-black surface has absorptivity α, it will absorb how much radiations?

α E_B

2 α E_B

3 α E_B

4 α E_B

Question 9 of 10

Question 10 of 10

10. The absorptivity of black body equals to

Question 10 of 10