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JEE Main · 2026 · 28 Jan 2026 · Shift 2 · Magnetic Effects of Current

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A long cylindrical conductor with large cross section carries an electric current distributed uniformly over its cross-section. Magnetic field due to this current is :
A. maximum at either ends of the conductor and minimum at the midpoint
B. maximum at the axis of the conductor
C. minimum at the surface of the conductor
D. minimum at the axis of the conductor
E. same at all points in the cross-section of the conductor

Choose the correct answer from the options given below :
  1. (A)D Only✓ Correct
  2. (B)A, D Only
  3. (C)B, C Only
  4. (D)E Only

Answer: (A)

Solution

For a long solid cylinder carrying current spread uniformly over its cross-section, Ampere's law on a circle of radius inside the conductor gives , so . The field thus grows linearly from zero on the axis to its largest value at the surface. Hence the magnetic field is minimum at the axis of the conductor, so statement D alone is correct.

JEE Main · 2026 · 28 Jan 2026 · Shift 2 · Single correct option

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