Thermal Equilibrium

What is Thermal Equilibrium
Thermal equilibrium follows the Zeroth Law of Thermodynamics. It explains the net heat transfer between two bodies that are kept in contact.

Everyone experiences heat whether they are near a flame, go outside in the sun, or sip from a hot cup of coffee. Similar to how we get a cold when we drink Pepsi or Coke, get into the bathtub, or go outside at night. Have you ever wondered why anything occurs like this? What do heat and cold actually mean? What connection do they have to temperature? What changes do our bodies make when we contact something that is hot or cold? All of this will be covered in this section under the subject of thermal equilibrium. Thermal equilibrium, to put it simply, offers a framework for establishing a relationship between heat and temperature. So let's get started right away! 

Heat is the energy transfer from a temperature that is high to one that is low. The system (or collection of systems) is considered to be in thermal equilibrium when these temperatures equalise and heat no longer flows through them. The absence of substance flowing into or out of the system is another implication of thermal equilibrium. Thermal equilibrium is a concept used in the zeroth law of thermodynamics to explain how two dissimilar systems may be stated to be at the same temperature. For instance, when molten lava rises from a volcano, heat is released into the air until both the rock and the air are the same temperature. Despite the stark differences between the two systems (rock and air), thermal equilibrium enables the determination of temperature for each.

Thermal equilibrium is the physical state of two bodies when they are connected by a permeable path, don’t undergo any heat transfer and both the bodies have the same temperature.