The generalized Maxwell equations in vacuum are basically the equations for steady states, which satisfy both energy and force conservation laws. However, superpositions of the steady states often break those conservation laws, although the generalized Maxwell equations are kept. To study those cases, we derived electromagnetic-dynamics equations, which include the generalized Maxwell equations, energy and force conservation laws, and dynamics of scalar fields. These equations explain that the scalar fields may work as the aether propagating the electromagnetic wave, and scalar waves may work as the gravitational waves.