Why there is no electric field due to the free charges of conductor although it is not placed in electric field? As we know that the conductor contains a lot of free charges positive as well negative. And also if it is placed inside the electric field the charges of conductor arranges themselves in such a way that they produce an equal and opposite induced electric field. This is what, when a conductor is placed in external electric field. But what about when a conductor does not placed into external electric field. I mean, let assume that a conductor is placed at vaccume. As, in this case also there is a lot  of positive and negative charges inside the conductor then why they do not create the electric field inside it ?? There also should be the electric field due to these charges but not. Why ??? This question has troubled me a lot and i'm searching for answer since last 2-3 days.
 A: Normally, any piece of material (conductor or not) has no net charge and no field (except on an atomic scale) .  For each proton there is an electron. Various techniques exist for adding or removing electrons from an object. Then it can produce an electric field.
A: There are fields inside a conductor! All of the particles within a conductor are producing their fields and interacting with each other. There are so many particles that the problem of calculating everything may seem completely intractable, but the solution emerged in the last century and forms the basis of solid state physics.
Why do you suppose the free electrons in a conductor are confined to the conductor? Why can’t they just float all around? The answer is that they are not really “free”, instead they occupy electron states within the conductor crystal that include interaction with all the other particles in the crystal. That is, “free electrons” are actually electrons which interact with everything in a particular way such that they appear free (they accelerate in an applied field, for example), but they’re still stuck inside the crystal. The existence of such states (at 0 Kelvin) is basically the definition of a conductor. 
As mentioned in another answer, there are an equal number of positive and negative charges in a neutral conductor. So, there is no net electric field generated by the whole thing. But if you were able to zoom in to the atomic scale, you’d find that indeed there are a lot of electric field variations. It’s just that those variations will all cancel out as you zoom out.
If you want to learn more, study solid state physics!
