For a uniformly charged thin spherical shell of radius R and total charge Q, the electric field INSIDE the shell (r < R) is:

Apply Gauss's law on a sphere of radius r < R inside the shell: **no charge enclosed → flux = 0 → E = 0**. **Outside the shell (r > R)**: shell behaves like a point charge at centre, E = kQ/r². **Just outside**: E = σ/ε₀ = kQ/R². NEET-favourite trap is testing inside-vs-outside.