ELECTRIC CHARGE AND FIELDS

[killershek]

In case of wire(having uniform linear charge density), without assuming the wire infinite long, why we can't take electric field perpendicular to the curved part of the cylindrical Gaussian surface?

 

[BvU]

Hello hek,

There's also field lines going in the direction along the cylinder (except in the symmetry plane perpendicular to the axis).

From very far away such a wire should look like a point charge and have the corresponding field. Only close by, the difference between infinitely long and just long is minimal.