The Full and Necessary Condition of the Electric Field of Mutual Parallel Field Lines Must Be Even Electric Field

It is proved that the size of electric field not change in vertical direction of electric field and can change in parallel direction of electric field for the electric field of mutual paralled field lines. It is proved that the region of existing surplus electric charges must be lion -- even electric field and the region of no existing surplus .electric charges must be even electric field for the electric field of mutual parallel field lines. This is the full and necessarg condition of that the electric field of mutual parallel field lines must be even electric field.