In an adiabatic process for an ideal gas, the pressure

Solution 30E First law of thermodynamics for a system is dq-dw=du In reversible adiabatic process dq=0 Therefore equation for this process is -dw=du When gas expands it do work i.e. dw= +ve therefore du = - ( +ve) du = -ve i.e change in internal energy = -ve internal energy decreasing or temperature is decreasing as internal energy is proportional to temperature only or roughly it is dependent to temperature Hence temperature is decreasing