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प्रश्न
Select the correct alternative
The vacuum kept in between the walls of a thermos flask reduces the heat transfer by
विकल्प
conduction only
convection only
radiation only
conduction and convection
उत्तर
conduction and convection
APPEARS IN
संबंधित प्रश्न
Give two examples each of conductors and insulators of heat.
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
Heat in a liquid is transferred by
State the direction of heat transfer by way of convection.
Explain briefly the process of heat transfer by radiation.
Give one example of heat transfer by radiation.
What are the modes of heat transfer?
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 |
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.
