A one-dimensional momentum conservation equation for a straight jet driven by an electrical field is developed.It is presented in terms of a stress component,which can be applied to any constitutive relation of fluids.The only assumption is that the fluid is incompressible.The results indicate that both the axial and radial constitutive relations are required to close the governing equations of the straight charged jet.However,when the trace of the extra stress tensor is zero,only the axial constitutive relation is required.It is also found that the second normal stress difference for the charged jet is always zero.The comparison with other developed momentum equations is made.