Karthik R

Hello @prajput

The main reason why the first law of thermodynamics is so important is because it enforces the principle of conservation of total energy in a system. It states that -

'There exists a variable of state, the internal energy ?. If a system is transformed from a state of equilibrium ? to another state ? by a process in which a certain amount of work ? is done by the surroundings, and a certain amount of heat ? being transferred from the surroundings, the difference in the internal energy of the systems is equal to the sum of ? and ?'

Hope that answers your question!