8:10:00 PM
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).
Thermal
Equilibrium:
- 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
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