Question

Can the electric field inside a conductor be non zero?

Answer 1

The hint to the above question lies in the word that is prefixed to the capacitor. Such capacitors have one of the measuring quantities which are held constant. The required value of the capacitance in such capacitors is achieved by varying the dielectric of the capacitor. Hence keeping the above key points in mind we can define a fixed capacitor

Complete step-by-step solution:
Consider a conductor neutral or charged. In a static situation, when there is no current inside or on the surface of the conductor the electric field is zero everywhere inside the conductor. A conductor has free electrons. As long as the electric field is not zero, the free charge carriers would experience force and drift. But we do not observe any field inside the conductor in a static situation as the free charges distribute themselves such that the electric field is zero everywhere inside.
Another approach to the above problem can be explained by the fact that excess charge can only reside on the surface of a charged conductor. Further if we enclose a volume element inside the conductor such that it does not enclose any part of the surface, the charge enclosed will be equal to zero. Hence the electric field at any point inside the conductor is zero.
Hence we can conclude that the electric field inside a conductor cannot be non zero.

Note: It is also to be noted that the electric field on the surface of the conductor is always normal to the surface. If the electric field is not normal and has some tangential component, then the field will drive the current on the surface of the conductor which is not observed. Electric field is nothing but a gradient of potential. Since the electric field is zero and no charge is enclosed and the electrostatic potential inside a conductor is constant.