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#boundary conditions

2 public questions tagged with this topic.

What causes the electric field to be discontinuous across a charged surface, such as a thin sheet?

**Line charge concept** extends point charge to infinite wire where symmetry dictates radial field proportional to λ and inversely proportional to distance r. λ = q/L for uniform case, field direction depends on sign of λ, outward for positive. The surface charge density on the sheet generates a field that changes abruptly. Gauss’s law shows the field on either side is sigma/2ε₀ , with opposite directions, resulting in a discontinuity equal to sigma/ε₀ across the surface. Substituting values gives Surface charge density, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.

Ref: NCERT > Physics Book > Electric Charges and Fields > Continuous Charge Distribution

What allows the electric field to be discontinuous across a charged surface, such as a conductor’s boundary?

**Charge conservation and quantization** govern rubbing processes where electrons transfer without creation. Total charge before and after remains equal, and any measured charge corresponds to n = q/e electrons, allowing counting of carriers from coulomb value. Surface charge density creates a field discontinuity. Inside a conductor, the field is zero, while just outside, it’s proportional to the surface charge density ( E = sigma/ε₀ ), as per Gauss’s law applied to a pillbox surface straddling the boundary. Substituting values gives Surface charge density, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.

Ref: NCERT > Physics Book > Electric Charges and Fields > Electric Charge, Quantization and Conservation