JEE Main 2026 — Magnetic Effects of Current Question with Solution

For a long cylindrical conductor with uniform current distribution, apply Ampere's law to find the magnetic field.
At distance $r$ from the axis (inside the conductor, $r<R$): $B(r)=\frac{{\mu }_{0}Ir}{2\pi R^2}$ (proportional to $r$)
At the axis ($r=0$): $B=0$ (minimum)
At the surface ($r=R$): $B=\frac{{\mu }_{0}I}{2\pi R}$ (maximum)
Analyzing the statements:
A. Maximum at ends and minimum at midpoint - FALSE. This describes behavior along the axis, but the magnetic field depends on radial distance, not axial position.
B. Maximum at the axis of the conductor - FALSE. The field is zero at the axis.
C. Minimum at the surface of the conductor - FALSE. The field is maximum at the surface.
D. Minimum at the axis of the conductor - TRUE. The field is zero at $r=0$, making it the minimum.
E. Same at all points in the cross-section - FALSE. The field varies from 0 at the axis to maximum at the surface.
Only D is correct.