In an adiabatic process for an ideal gas, the pressure decreases. In this process does the internal energy of the gas increase or decrease? Explain your reasoning.
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