Advertisements
Advertisements
प्रश्न
Why are the houses in Rajasthan painted white?
Advertisements
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
Give two examples each of conductors and insulators of heat.
Fill in the blank
Heat transfer in liquids and gases is by ________.
Select the correct alternative
Heat in a liquid is transferred by
Give one example of heat transfer by radiation.
How does a fever get lowered by putting a cold compress on the forehead of a patient?
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 |
When ice changes into a liquid, it absorbs energy.
When a liquid boils, energy is absorbed.
Take a sheet of paper. Draw a spiral on it as shown in Figure. Cut out the paper along the line. Suspend the paper as shown in Figure above a lighted candle. Observe what happens. Think of an explanation.

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.
