Advertisements
Advertisements
प्रश्न
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.
उत्तर
- When you wrap a thin paper strip tightly around an iron rod and try to burn it with a candle while rotating the rod continuously, the paper does not burn.
- This is because the iron rod absorbs and conducts away the heat from the candle flame, preventing the paper from reaching its ignition temperature.
- The continuous rotation ensures that no single part of the paper is exposed to the flame long enough to catch fire.
संबंधित प्रश्न
No medium is required for transfer of heat by the process of ______.
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.
Liquids are heated by conduction and radiation.
Write true or false for a given statement.
Black surfaces are the poor absorbers of heat radiations.
Fill in the blank
Heat transfer in solids is by ______
Give one example of heat transfer by radiation.
Maximum heat is absorbed by a ______ coloured object.
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.
