## 2008-06-02

### Understanding Thermal equilibrium

It has to be noted that temperature is one of the basic quantities in physics.

Temperature is a physical quantity which measures the DEGREE of HOTNESS of an object. So as you probably have inferred, hot object has a higher temperature than a cold object.

The SI unit of temperature is Kelvin, K. Other units such as degree Celcius (centigrade) and Fahrenheit is also used.

When two objects are in thermal contact, heat is transferred from one object to the other.

The temperature of the objects determines the direction of energy transfer between them. The energy transferred between objects in thermal contact is known as heat.

Let say there are two objects A and B.

Say A has higher temperature than B. When A and B is in contact with each other, heat will be transferred from A to B. That is A will give heat and B will receive heat. When this situation occurs, it is called net heat transfer from A to B.

The heat transfer will continue until a state of thermal equilibrium is achieved.

It is expected that temperature of B will rise to a certain degree (due to increased kinetic energy in the molecules), when thermal equilibrium is achieved and temperature A will fall. At the end of transfer, both A and B will have the same temperature.

Heat

Heat is a form of energy. The SI unit for heat is joule, J.

Heat is produced by mechanical energy or from the conversion of other types of energy. such as electrical energy to heat energy and so on.

It must be noted that Temperature is NOT the same as Heat.

Temperature is a measure of degree of hotness of an object, is a base quantity, SI unit is kelvin and other units are degree celcius and fahrenheit. It determines the direction of heat flow.

Heat is a form of energy, is a derived quantity and SI unit is Joule, J. (other unit is calorie, cal.) It is being transferred from a region of higher temperature to another region of lower temperature.

Hope this does not confuse you! 