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Many physical systems, including mechanical, electrical, electromechanical, fluid, and thermal systems, can be modeled by the Langrangian and Hamiltonian equations of motion. A key aspect of the Langrangian and Hamiltonian frameworks is the role of energy storage. In this paper, equations regarding Langrangian and Hamiltonian are discussed and compared to the Brayton-Moser equations. A practical advantage of the BM framework is that the system variables are directly expressed in terms of easily measurable quantities, such as currents, voltages, velocities, forces, volume flows, pressures, or temperatures. The Langrangian, and Hamiltonian formulation normally involve generalized displacement and momenta, which in many cases cannot be measured directly.