8, జులై 2016, శుక్రవారం
- 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.
- 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.