Hotness,
Coldness:
- When heat energy flows out of
our body to any substance we get the feeling of coldness.
- For example, due to the heat
energy is being transferred from our body to soft cold drink bottle which take
out from fridge, we feel it as cold.
- When heat energy enters our
body (we get) from any substance we get a feeling of hotness.
- When we touch the vessel kept on
the stove, we feel the vessel hot because the heat energy transferred from the
vessel to our body.
Comparison
of Hotness and Coldness: (or)
Finding
of intensity of Heat energy:
1. Keep wooden piece and iron
piece or metal piece in a fridge or ice box for 15 minutes.
2. After take them out and touch,
we feel they are cold.
3. We feel that the metal piece
is colder than the wooden piece.
4. That means more heat energy
flows out of our body when we touch the metal piece as compared to the wooden
piece.
5. This means, the “degree of
coldness” of the metal piece is less than that of the wooden piece.
Temperature:
- The degree of hotness or
coldness is called temperature.
- (or) the intensity of heat is
called temperature.
- The unit of temperature is
degree Celsius (0C), In SI system the unit is Kelvin (K).
Kelvin scale
– Celsius Scale:
- The S.I. unit of temperature is
Kelvin (K).
- 00 C = 273 K
- Kelvin denotes as ‘K’, not as ‘0K’.
Temperature
in Kelvin = 273 + temperature in degree Celsius
t0
C = (273 + t) K
- To get the temperature on the Kelvin
scale, add 273 to the value of the temperature in degree Celsius.
- Temperature, measured on Kelvin
scale is called absolute temperature.
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