MCQOPTIONS
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MCQOPTIONS
This section includes 13 Mcqs, each offering curated multiple-choice questions to sharpen your Heat Transfer knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A gray body (E = 0.8) emits the same amount of heat as a black body at 1075 K. Find out the required temperature of the gray body |
| A. | 1146.72 K |
| B. | 1136.72 K |
| C. | 1126.72 K |
| D. | 1116.72 K |
| Answer» C. 1126.72 K | |
| 2. |
For a hemisphere solid angle is measured as |
| A. | Radian and its maximum value is π |
| B. | Degree and its maximum value is 180 degree |
| C. | Steradian and its maximum value is 2π |
| D. | Steradian and its maximum value is π |
| Answer» E. | |
| 3. |
The monochromatic emissivity € of a diffuse surface at 1600 K varies with wavelength in the following manner€ = 0.4 for 0 < λ < 2 = 0.8 for 2 < λ < 5Determine the total emissivity |
| A. | 0.5558 |
| B. | 0.5568 |
| C. | 0.5578 |
| D. | 0.5588 |
| Answer» D. 0.5588 | |
| 4. |
The radiant heat transfer from a plate of 2.5 cm2 area at 1250 K to a very cold enclosure is 5.0 W. Determine the emissivity of the plate at this temperature |
| A. | 0.444 |
| B. | 0.344 |
| C. | 0.244 |
| D. | 0.144 |
| Answer» E. | |
| 5. |
FOR_A_HEMISPHERE_SOLID_ANGLE_IS_MEASURED_AS?$ |
| A. | Radian and its maximum value is π |
| B. | Degree and its maximum value is 180 degree |
| C. | Steradian and its maximum value is 2π |
| D. | Steradian and its maximum value is π |
| Answer» E. | |
| 6. |
A_gray_body_(E_=_0.8)_emits_the_same_amount_of_heat_as_a_black_body_at_1075_K._Find_out_the_required_temperature_of_the_gray_body$ |
| A. | 1146.72 K |
| B. | 1136.72 K |
| C. | 1126.72 K |
| D. | 1116.72 K |
| Answer» C. 1126.72 K | |
| 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 |
| A. | 0.98 * 10 <sup>-4</sup> m<sup>2</sup> |
| B. | 1.98 * 10 <sup>-4</sup> m<sup>2</sup> |
| C. | 2.98 * 10 <sup>-4</sup> m<sup>2</sup> |
| D. | 3.98 * 10 <sup>-4</sup> m<sup>2</sup> |
| Answer» B. 1.98 * 10 <sup>-4</sup> m<sup>2</sup> | |
| 8. |
The radiant heat transfer from a plate of 2.5 cm2 area at 1250 K to a very cold enclosure is 5.0 W. Determine the emissivity of the plate at this temperature |
| A. | 0.444 |
| B. | 0.344 |
| C. | 0.244 |
| D. | 0.144 |
| Answer» E. | |
| 9. |
If a black body at 1000 K and a gray body at 1250 K emit the same amount of radiation, what should be the emissivity of the gray body? |
| A. | 0.3096 |
| B. | 0.4096 |
| C. | 0.5096 |
| D. | 0.6096 |
| Answer» C. 0.5096 | |
| 10. |
The emissivity of the gray surface may be expressed as |
| A. | σ /2 σ <sub>b</sub> |
| B. | σ / 3 σ <sub>b</sub> |
| C. | σ / σ <sub>b</sub> |
| D. | ½ σ / σ <sub>b</sub> |
| Answer» D. ¬¨¬®≈í¬© ‚âà√¨‚àö√¢ / ‚âà√¨‚àö√¢ <sub>b</sub> | |
| 11. |
When the emissivity of non-black surface is constant at all temperatures and throughout the entire range of wavelength, the surface is called |
| A. | Gray body |
| B. | Transparent body |
| C. | Opaque bodies |
| D. | Perfect black body |
| Answer» B. Transparent body | |
| 12. |
When Stefan-Boltzmann law is applied to a black body, it takes the form |
| A. | E = σ T |
| B. | E = σ T <sup>2</sup> |
| C. | E = σ T <sup>3</sup> |
| D. | E = σ T <sup>4</sup> |
| Answer» E. | |
| 13. |
Consider two bodies, one absolutely back and the other non-black and let these be at same temperature. Which one of the following statement is correct? |
| A. | Black body radiates less intensively than a non-black body |
| B. | Non-black body radiates less intensively than a black body |
| C. | Both will radiates equally |
| D. | None of them will radiates |
| Answer» C. Both will radiates equally | |