Thermodynamics and Thermodynamics laws - First law of thermodynamics - Zeroth law of thermodynamics

Thermodynamics and Thermodynamics laws

                  Heat and temperature play a vital role in our daily life. We should study heat and thermodynamics because thermodynamics is used to apply mechanical engineering. When an object at a higher temperature is placed in contact with another object at a lower temperature, the flow of energy from the object at a higher temperature to a lower temperature, this energy transfer is called heat. Usually, the temperature is measured in Celsius (C) and Fahrenheit (^oF) scales but the SI unit of temperature is Kelvin (K).

The first law of Thermodynamics  

           Thermodynamics laws are used to understand engines. This first law of thermodynamics is a statement of the law of conservation of energy. This conservation of energy usually involves kinetic energy and potential energy of bulk objects.

Change in internal energy (∆U) of the system is equal to heat supplied to the system (Q) is subtracted from the work done by the system (W).

∆U = Q – W

·       If heat flows into the system the internal energy will increase.

·       If heat flows out of the system the internal energy will decrease.

·       If work is done on the system the internal energy will increase.

·       If work is done by the system the internal energy will decrease.

Zeroth law of Thermodynamics 

While we read this zeroth law of thermodynamics we think about why? This name is suit for the thermodynamics law. The reason is scientists found the first law of thermodynamics and next they found this law but this law is very basic for the first law of thermodynamics so that scientists named it the Zeroth law of thermodynamics.  

This law states that, If two systems, A and B are in thermal equilibrium with a third system C. Then A and B are in thermal equilibrium with each other.

Consider three systems A, B and C which are initially at different temperatures. To understand this Zeroth law we assume that systems A and B are not in contact with each other. But system C is in thermal contact with each other. This consideration system A and B will be thermal equilibrium with system C. Finally three systems are at thermal equilibrium there will be no heat flow between them as they are at the same temperature. This law is used to measure the temperature of the human body.

       This law enables us to determine the temperature of any system.  For instance, when a thermometer is kept in contact with a human body, it reaches thermal equilibrium with the body. This means the temperature of the thermometer will be the same as the human body. So mercury indicates temperature level at remaining some time.