Question

Explain the formulation of first law of thrmodynamics.

Answer 1

1. The first law of thermodynamics is simply the principle of conservation of energy.
2. If Q is heat supplied to the system and if W work is done on the system by the surroundings. The internal energy of the system would increase ΔU.
3. From the conservation of energy we can write,
   increase in internal energy of the system
    = Quantity of heat absorbed by the system + Work done on the system
   ∴ Δ U = Q + W
   For an infinitesimal change,
   dU = dQ + dW