  Although entropy is a necessary and sufficient quantity to characterize the
order of work content for equal energetic (EE) states in the asymptotic limit,
for the finite quantum systems, the relation is not so linear and requires
detail investigation. Toward this, we have considered a resource theoretic
framework taking the energy preserving operations (EPO) as free, to compare the
amount of extractable work from two different quantum states. Under EPO,
majorization becomes a necessary criterion for state transformation. It is also
shown that the passive state energy is a concave function and for EE states it
becomes proportional to the ergotropy in absolute sense. Invariance of the
passive state energy under unitary action on the given state makes it an
entanglement measure for the pure bipartite states. Further, due to the non
additivity of passive state energy for the different system Hamiltonians, one
can generate Vidal's monotones which would give the optimal probability for
pure entangled state transformation. This measure also quantifies the
ergotropic gap which is employed to distinguish some specific classes of
three-qubit pure entangled states.
