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प्रश्न
Why does the bottom of a lake not freeze in severe winter though the surface is all frozen?
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उत्तर
Lakes don’t completely freeze because the ice (and eventually snow) on the surface acts to insulate die water below. To freeze water into ice, a large quantity of heat is to be withdrawn. This heat cannot be
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संबंधित प्रश्न
Match the following
| Column A | Column B |
| 1. mercury | 1. insulator |
| 2. wood | 2. water from 0°C to 4°C |
| 3. Aluminum | 3.absorbs |
| 4. contracts | 4.conductor |
| 5.black surface | 5. Thermometer |
Fill in the blank and rewrite the sentence.
If objects of equal masses are given equal heat, their final temperature will be different. This is due to difference in their ................. .
What will absorb heat?
Iron griddle (tava)
Name the SI unit of heat.
1 calorie is 4.81 joules.
______ energy can be generated by the burning of fuels like coal, wood, charcoal, gasoline, etc.
Analogy:
Movement of molecules:: Heat.
Heat energy:: ______.
In the arrangements A and B shown in the following figure, pins P and Q are fixed to a metal loop and an iron rod with the help of wax. In which case are both the pins likely to fall at different times? Explain.
Assertion: Small gaps left between railway lines.
Reason: It allows for the contraction of rails during summer.
