Physics · Electrostatic Potential And Capacitance · NEET
Yes, in the static (settled) state. Free electrons move until they arrange themselves so their own field exactly cancels any applied field. Any leftover field would push charges again, so it cannot stay. Once things are at rest, E = 0 at every interior point. This is the parent rule that gives all the other conductor properties.
Use Gauss's law. Take a Gaussian surface just inside the conductor. Since E = 0 there, the flux is zero, so the enclosed charge is zero. This is true for any interior point, so no net charge can live in the bulk. Extra charge is forced to the outer surface, where it spreads out.
Because E = 0 inside and E is tangential-zero on the surface. Potential difference = work to move a charge = integral of E. If E = 0 along any inside path, no work is done, so every interior and surface point sits at one potential. A conductor is an equipotential body. This is why the NEET 2024 shell question gives delta V = 0 between two inside points.
If the field had a sideways (tangential) part along the surface, it would push the free surface charges sideways and they would keep moving. In the static state nothing moves, so the tangential part must be zero. Only the normal part survives, giving E = sigma/epsilon0 pointing straight out of (or into) the surface.
If the cavity holds NO charge, yes, the field inside the cavity is zero too. This is electrostatic shielding (the idea behind a Faraday cage). But if you place a charge Q inside the cavity, the field in the cavity is NOT zero, an induced -Q appears on the cavity wall, and +Q spreads on the outer surface. That is exactly the ReNEET 2026 cavity trap.
Which of the following statements are correct? A. Inside a conductor, the electrostatic field is zero. B. Electric field at the surface of a charged conductor does not depend on its surface charge density. C. The interior of a charged conductor can have no excess charge in the static situation. D. At the surface of a charged conductor, the electrostatic field must be normal to the surface at every point. E. The electrostatic potential is zero everywhere inside a charged conductor.
A thin spherical shell is charged by some source. The potential difference between two points C and P, both inside the shell, is (Take 1/(4*pi*epsilon0) = 9 x 10^9 SI units):
A point charge Q is placed inside a cavity within a solid isolated conducting sphere. Consider point A (inside the cavity), and points B and C (outside the sphere, equidistant from its centre) with field magnitudes E_A, E_B, E_C. The correct option is:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Six rules: (1) field inside is zero, (2) field just outside is normal to the surface, (3) the whole conductor is at one potential (equipotential), (4) any excess charge lives only on the outer surface, (5) surface field E = sigma/epsilon0, (6) a charge-free cavity has zero field (shielding).
No. The potential inside a conductor is CONSTANT and equals the surface value, but that constant is usually not zero. Only the electric field is zero inside; do not confuse zero field with zero potential.
It is normal (perpendicular) to the surface with magnitude E = sigma/epsilon0, where sigma is the local surface charge density. Sharper points have higher sigma, so they have a stronger field, which is why charge leaks from pointed tips.
A charge-free cavity inside a conductor has zero field no matter what fields exist outside. The conductor shields its inside from external fields. This is the principle of a Faraday cage. But a charge placed inside the cavity does create a field within the cavity.
Apply Gauss's law to a surface just inside the conductor. Since E = 0 there, the enclosed charge is zero, so no net charge can sit in the interior. All extra charge is pushed to the outer surface where like charges spread as far apart as possible.
