Thermal Energy Transfer and Equilibrium
Thermal Energy Transfer and Equilibrium
Put two objects in thermal contact. Temperature tells you which way thermal energy is transferred.
Temperature gives the direction
Thermal energy is transferred from the object at the higher temperature to the object at the lower temperature. The transfer continues while their temperatures are different.
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Key idea
Thermal equilibrium
The final condition is called .
Definition
2 marksWhat is meant by thermal equilibrium?
Model answer: Two objects are in thermal equilibrium when they have the same temperature and there is no net transfer of thermal energy between them.
Net means the overall result. At equilibrium, neither object gains thermal energy overall. A complete exam answer needs both marking points (9702/42/F/M/25 Q3(a)(i)) (9702/42/O/N/25 Q3(a)).
A thermometer and some water both read 25 °C. What two statements show that they are in thermal equilibrium?
Show worked answer
They have the same temperature, and there is no net transfer of thermal energy between them.
First identify the higher temperature. Then state the direction of transfer. At equilibrium, state equal temperature and no net transfer.