Abstract
The kinetic energy of a charged system is calculated for Mermin's one-particle density matrix of Fermi superfluids. The final expression consists of two separate contributions from the center-of-mass and the relative motions of an effective bound-state wave function. The relative part naturally includes coupling of the intrinsic orbital angular momentum density to the magnetic field. For 3 He- A at T =0, its magnitude is \((\hbar / 2) \times \)(number density), in agreement with Ishikawa's result.