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प्रश्न
Why are the houses in Rajasthan painted white?
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उत्तर
White colours are reflectors of heat. Thus, Rajasthan, a very hot state, has houses with their walls painted white so that most of the heat from the sun is reflected back to the atmosphere. This keeps the houses cool from inside.
संबंधित प्रश्न
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.
On touching a lump of ice, we feel cold because some heat passes from our body to the ice.
Write true or false for a given statement.
Medium is necessary for the transfer of heat by radiation.
Fill in the blank
A hot metallic piece is placed in tap water contained in a bucket. Heat will flow from _______ to _________
Fill in the blank
Heat transfer in liquids and gases is by ________.
State the direction of heat transfer by way of convection.
How does a fever get lowered by putting a cold compress on the forehead of a patient?
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.
