The work done by an electric field is defined as N, while the work done by an external force moving against the field is negative N. When moving an object in the same direction as the electric field, the total work is not zero, and the object's kinetic energy will increase. If the external force assists the electric field, it can either slow the particle down or accelerate it beyond the field's influence. The work performed by the external force is equal to the difference between the final kinetic energy and the kinetic energy that would have been achieved without interference. This highlights the interplay between external forces and electric fields in determining work and energy changes.