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PHYSICS BLOG ON TRANSFER OF THERMAL ENERGY! (:
Tuesday, June 9, 2009
What Causes Transfer of Thermal Energy?
- Thermal energy is transferred only when there is a difference in temperature.
- Thermal energy always flows from a region of higher temperature to a region of lower temperature until the two objects reach the same final temperature.
Experiment 1 (:
Temperatures of the basins.- Cold: 10° C
- Warm: 37°C
- Hot: 70°C
Step 1:
When you place your left hand in the hot water basin, it feels hot because it gains thermal energy from the hot water.
Step 2:
When you place your right hand in the cold water basin, it feels cold because it loses thermal energy to the cold water.
Step 3:
After removing your hands and drying them with a cloth, when the effects of hotness and coldness in your hands has subside, place your hand in the warm water basin. As your hands feel neither hot nor cold as there is thermal equilibrium. As such, there is no net gain or loss of thermal energy between the water in the warm water basin and your hands.
Alternatively, you can replace step 3 with this.
Step 3:
After putting your hands in the respective basins after a period of time, remove your hands and immediately place your hands into the warm water basin. Your left hand would feel that the water is cooler while your right hand would feel that the water is warmer. Why is this so?
-Your left hand, which was in the hot water basin, transferred heat between the water and your hand until there was thermal equilibrium. Therefore, the temperature of your hand would be higher than it was in the beginning. As such, when you place your hand in the warm water basin, which is about the normal temperature of human beings, the warm water would quickly conduct the heat away, which leaves us with a cooling effect.
-Your right hand, which was in the cold water basin, transferred heat between the water and your hand until there was thermal equilibrium. Therefore, the temperature of your hand would be lower than it was in the beginning. As such, when you place your hand in the warm water basin, which is about the normal temperature of human beings, heat from the warm water would be conducted towards the hand suddenly, which leaves us with a hot sensation.
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