In such electromagnetic thrusters, the working fluid is most of the time ionized hydrazine, xenon or lithium. Depending on the propellant used, it can be seeded with alkali such as potassium or caesium to improve its electrical conductivity. All charged species within the plasma, from positive and negative ions to free electrons, as well as neutral atoms by the effect of collisions, are accelerated in the same direction by the Lorentz "body" force, which results from the combination of a magnetic field with an orthogonal electric field (hence the name of "cross-field accelerator"), these fields not being in the direction of the acceleration. This is a fundamental difference with ion thrusters which rely on electrostatics to accelerate only positive ions using the Coulomb force along a high voltage electric field.