Joule's Law and Enthalpy - Thermodynamics:
Joule's Law
Joules law experiment is based on the constant volume process, and it state that I.E. of perfect gas is a function of absolute temperature only.That is,
U = f(T)
dU = dQ - dW; It define constant volume that is dw = 0 dU = dQ; but dQ = mC_{v}dT, at constant volume
dU = mC_{v}dT; for a perfect gas
Enthalpy
It is sum of I.E. (U) and pressure - volume product.
H + pv
For unit mass pv =RT
h = C_{V}T + RT = (C_{V} + R)T = C_{P}T = (dQ)_{P}
H = mC_{P}T
dH = mC_{P}dT