MCQOPTIONS
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MCQOPTIONS
This section includes 16 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 metal sphere of surface area 0.0225 m2 is in an evacuated enclosure whose walls are held at a very low temperature. Electric current is passed through resistors embedded in the sphere causing electrical energy to be dissipated at the rate of 75 W. If the sphere surfaces temperature is measured to be 560 K, while in steady state, calculate emissivity of the sphere surface |
| A. | 0.498 |
| B. | 0.598 |
| C. | 0.698 |
| D. | 0.798 |
| Answer» C. 0.698 | |
| 2. |
A furnace emits radiation at 2000 K. Treating it as a black body radiation, calculate the monochromatic radiant flux density at 1 micron m wavelength |
| A. | 5.81 * 10 7 W/m2 |
| B. | 4.81 * 10 7 W/m2 |
| C. | 3.81 * 10 7 W/m2 |
| D. | 2.81 * 10 7 W/m2 |
| Answer» E. | |
| 3. |
Planck’s law is given by |
| A. | (E) b = 2 π c 2 h (Wavelength) -5/[c h/k (Wavelength) T] – 2 |
| B. | (E) b = π c 2 h [exponential [c h/k (Wavelength) T] – 3]. |
| C. | (E) b = 2 π c 2 h (Wavelength) -5/exponential [c h/k (Wavelength) T] – 1 |
| D. | (E) b = 2 c 2 h (Wavelength) -5/exponential [c h/k (Wavelength) T] – 6 |
| Answer» D. (E) b = 2 c 2 h (Wavelength) -5/exponential [c h/k (Wavelength) T] – 6 | |
| 4. |
The Planck’s constant h has the dimensions equal to |
| A. | M L 2 T -1 |
| B. | M L T -1 |
| C. | M L T -2 |
| D. | M L T |
| Answer» B. M L T -1 | |
| 5. |
The sun emits maximum radiation of 0.52 micron meter. Assuming the sun to be a black body, Calculate the emissive ability of the sun’s surface at that temperature |
| A. | 3.47 * 10 7 W/m2 |
| B. | 4.47 * 10 7 W/m2 |
| C. | 5.47 * 10 7 W/m2 |
| D. | 6.47 * 10 7 W/m2 |
| Answer» D. 6.47 * 10 7 W/m2 | |
| 6. |
A small body has a total emissive power of 4.5 kW/m2. Determine the wavelength of emission maximum |
| A. | 8.46 micron m |
| B. | 7.46 micron m |
| C. | 6.46 micron m |
| D. | 5.46 micron m |
| Answer» E. | |
| 7. |
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. | A sin α |
| B. | A cos α |
| C. | 2A cos α |
| D. | 2A cos α |
| Answer» C. 2A cos α | |
| 8. |
A_METAL_SPHERE_OF_SURFACE_AREA_0.0225_M2_IS_IN_AN_EVACUATED_ENCLOSURE_WHOSE_WALLS_ARE_HELD_AT_A_VERY_LOW_TEMPERATURE._ELECTRIC_CURRENT_IS_PASSED_THROUGH_RESISTORS_EMBEDDED_IN_THE_SPHERE_CAUSING_ELECTRICAL_ENERGY_TO_BE_DISSIPATED_AT_THE_RATE_OF_75_W._IF_THE_SPHERE_SURFACES_TEMPERATURE_IS_MEASURED_TO_BE_560_K,_WHILE_IN_STEADY_STATE,_CALCULATE_EMISSIVITY_OF_THE_SPHERE_SURFACE?$ |
| A. | 0.498 |
| B. | 0.598 |
| C. | 0.698 |
| D. | 0.798 |
| Answer» C. 0.698 | |
| 9. |
A_FURNACE_EMITS_RADIATION_AT_2000_K._TREATING_IT_AS_A_BLACK_BODY_RADIATION,_CALCULATE_THE_MONOCHROMATIC_RADIANT_FLUX_DENSITY_AT_1_MICRON_M_WAVELENGTH?$ |
| A. | 5.81 * 10<sup> 7 </sup>W/m<sup>2</sup> |
| B. | 4.81 * 10<sup> 7 </sup>W/m<sup>2</sup> |
| C. | 3.81 * 10<sup> 7 </sup>W/m<sup>2</sup> |
| D. | 2.81 * 10<sup> 7 </sup>W/m<sup>2</sup> |
| Answer» E. | |
| 10. |
Planck’s law is given b?# |
| A. | (E) <sub>b </sub>= 2 π c<sup> 2 </sup>h (Wavelength)<sup> -5</sup>/[c h/k (Wavelength) T] – 2 |
| B. | (E) <sub>b </sub>= π c<sup> 2 </sup>h [exponential [c h/k (Wavelength) T] – 3]. |
| C. | (E) <sub>b </sub>= 2 π c<sup> 2 </sup>h (Wavelength)<sup> -5</sup>/exponential [c h/k (Wavelength) T] – 1 |
| D. | (E) <sub>b </sub>= 2 c<sup> 2 </sup>h (Wavelength)<sup> -5</sup>/exponential [c h/k (Wavelength) T] – 6 |
| Answer» D. (E) <sub>b </sub>= 2 c<sup> 2 </sup>h (Wavelength)<sup> -5</sup>/exponential [c h/k (Wavelength) T] ‚Äö√Ñ√∂‚àö√ë‚àö¬® 6 | |
| 11. |
The Planck’s constant h has the dimensions equal to$ |
| A. | M L <sup>2 </sup>T <sup>-1</sup> |
| B. | M L T <sup>-1</sup> |
| C. | M L T <sup>-2</sup> |
| D. | M L T |
| Answer» B. M L T <sup>-1</sup> | |
| 12. |
The law governing the distribution of radiant energy over wavelength for a black body at fixed temperature is referred to as |
| A. | Kirchhoff’s law |
| B. | Planck’s law |
| C. | Wein’s formula |
| D. | Lambert’s law |
| Answer» C. Wein‚Äö√Ñ√∂‚àö√ë‚àö¬•s formula | |
| 13. |
The sun emits maximum radiation of 0.52 micron meter. Assuming the sun to be a black body, Calculate the emissive ability of the sun’s surface at that temperature$ |
| A. | 3.47 * 10 <sup>7 </sup>W/m<sup>2</sup> |
| B. | 4.47 * 10 <sup>7 </sup>W/m<sup>2</sup> |
| C. | 5.47 * 10 <sup>7 </sup>W/m<sup>2</sup> |
| D. | 6.47 * 10 <sup>7 </sup>W/m<sup>2</sup> |
| Answer» D. 6.47 * 10 <sup>7 </sup>W/m<sup>2</sup> | |
| 14. |
A small body has a total emissive power of 4.5 kW/m2. Determine the wavelength of emission maximum |
| A. | 8.46 micron m |
| B. | 7.46 micron m |
| C. | 6.46 micron m |
| D. | 5.46 micron m |
| Answer» E. | |
| 15. |
Likewise the amount of emitted radiation is strongly influenced by the wavelength even if temperature of the body is |
| A. | Constant |
| B. | Increasing |
| C. | Decreasing |
| D. | It is not related with temperature |
| Answer» B. Increasing | |
| 16. |
The energy emitted by a black surface should not vary in accordance with |
| A. | Wavelength |
| B. | Temperature |
| C. | Surface characteristics |
| D. | Time |
| Answer» E. | |