Q.87 According to first law of thermodynamics (a) total internal energy of a system during a process remains constant (b) total energy of a system remains constant (c) work done by a system is equal to the heat transferred by the system (d) internal energy, enthalpy and entropy during a process remains constant hence it is an Isochoric process. Q.88 Internal energy is defined by (a) Zeroth law of thermodynamics (b) First law of thermodynamics (c) Second law of thermodynamics (d) Law of entropy Q.89 Key concept in analyzing the filling of an evacuated tank is (a) the mass flow rate in the tank remains constant (b) the enthalpy across the valve remains constant (c) the internal energy in the tank remains constant (d) the temperature in the tank remains constant