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प्रश्न
______ of heat does not require a medium.
विकल्प
radiation
white
conduction
blue
convection
bad conductor
good conductor
black
reflection
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उत्तर
Convection of heat does not require a medium.
Explanation:
In convection, when the temperature of a substance increases due to heat, its molecules move faster, causing them to rise. As a result, cooler and denser objects sink to the bottom. This process is possible only when a substance (liquid or gas) is present, as it requires the mobility and movement of molecules.
संबंधित प्रश्न
No medium is required for transfer of heat by the process of ______.
Look at Figure. Mark where the heat is being transferred by conduction, by convection and by radiation.
Write true or false for a given statement.
Medium is necessary for the transfer of heat by radiation.
Write true or false for a given statement.
Black surfaces are the poor absorbers of heat radiations.
Select the correct alternative
The vacuum kept in between the walls of a thermos flask reduces the heat transfer by
Explain briefly the process of heat transfer by radiation.
Match the items in column-I to the items in column-II
| Column-I | Column-II | ||
| 1. | Linear expansion | (a) | change in volume |
| 2. | Superficial expansion | (b) | hot body to cold body |
| 3. | Cubical expansion | (c) | 1.381 X 10-23 JK-1 |
| 4. | Cubical expansion | (d) | change in length |
| 5. | Boltzmann constant | (e) | change in area |
The handles of cooking utensils are made of ______.
Wrap a thin paper strip tightly around an iron rod. Try to burn the paper with candle while rotating the iron rod continuously. Does it burn? Explain your observation.
Take two similar transparent glass bottles having wide mouths. Put a few crystals of potassium permanganate or pour a few drops of ink in one bottle. Fill this bottle with hot water. Fill the other bottle with cold water. Cover the cold water bottle with a thick piece of paper such as a postcard. Press the postcard firmly with one hand and hold the bottle with the other hand. Invert the bottle and place it on top of the hot water bottle. Hold both the bottles firmly. Ask some other person to pull the postcard. Observe what happens. Explain.
