7, జులై 2016, గురువారం
Heat – Activity on transfer of heat:
1. Take two glass tumblers, one filled with hot water and another with cold water.
2. Keep a laboratory thermometer in hot water tumbler at first.
3. We observe that there is a raise in mercury level.
4. Because heat got transferred from the hotter body (hot water) to the colder body (mercury in the thermometer).
5. Next, place the thermometer in cold water tumbler and observe.
6. We observe that the mercury level comes down
7. Because the heat energy transferred from hotter body (mercury) to the colder body (cold water).
8. Heat is a form of energy in transit that flows from a body at higher temperature to a body at lower temperature.
9. Heat is a form of energy that transfer from hotter body to colder body.
Another activity on transfer of heat energy:
1. Take 600 C hot water in a cylindrical transparent glass jar.
2. Gently pour coconut oil over the surface of the water.
3. Put two holed lid on it and insert two thermometers in the holes.
4. Insert one of the thermometers lies only in the water and other only in coconut oil.
5. Then we observe that, the reading of the thermometer kept in water decreases, at the same time the reading of the thermometer kept in oil increases.
6. That means, the heat energy flows from the hot water (hot body) to coconut oil (cold body).
- When two bodies are placed in thermal contact, then energy will be transferred from the ‘hotter’ body to the ‘colder’ body.
- Transfer of heat energy continuous till both bodies attain the same degree of hotness (or) coldness.
- When two bodies attain same degree of hotness (or) coldness, transfer of heat energy stops.
- The state of thermal equilibrium denotes a state of a body where it neither receives nor gives out heat energy.
- When two bodies are at same temperature and in contact, Thermal equilibrium takes place.
Hotness and Coldness of our surroundings:
- If we feel hot in our surroundings, the heat energy transferred from surroundings to our body.
In this case: Colder body – our Body
Hotter body – Surroundings.
- If we feel cold in our surroundings, the heat energy transferred from our body to surroundings.
In this Case: Colder body – surroundings
Hotter body – Our body