Question

State first law of thermodynamics and derive the relation between the change in internal energy (∆U), work done (W) and heat (Q).​

Answer 1

Answer:

The first law of thermodynamics states that the change in internal energy of a system equals the net heat transfer into the system minus the net work done by the system. In equation form, the first law of thermodynamics is ΔU = Q − W. Here ΔU is the change in internal energy U of the system.

Answer 2

Answer:

1) When the amount of heat Q is added to system and system does not do any work during the process, its internal energy increases by the amount

                                             delta U = Q

2) When the system does some work to increase its volume and no heat is added to it while expanding, the system loses energy to its surrounding and its internal energy decreases.

                                            delta U = -W

3) As the internal energy can be changed using both ways, we can consider the total change in internal energy as

                                            delta U = Q-W