We all know that speed of light can not be exceeded. So the question is if electric field accelerates electron in a vacuum tube with enormous length won't the electron accelerate till a point where it overcomes the speed of light? The same question applies for electrons flowing in materials in superconductive state isn't the resistance zero which means there is nothing that can deccelerate them? I know that many of you will find this question stupid but I'm very curious because this is not the kind of questions that bring professors up in classes.
You would need to supply an infinite amount of energy to an electron (or any massive particle) to accelerate it to the speed of light. The (theoretical) absence of a decelerating force simply implies that the electrons won't slow down once they have been accelerated to a certain velocity.