A long cylindrical conductor with large cross section carries an… | JEE Main 2026 (28 Jan, Shift 2)

Q4JEE Main 2026 · 28 JAN · SHIFT 2Easy

Ampere's Law, Cylinders, Solenoid & Toroid

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:

Show answer and solution

Answer: (d)

Ampere's law inside a uniformly carrying cylinder: $B = \dfrac{\mu_0 I r}{2\pi R^2}$ for $r \le R$ .
At the axis $r = 0$ , so $B = 0$ (minimum). D is true; B is false.
$B$ grows with $r$ and is maximum at the surface $r = R$ , so C and E are false.
For a long conductor the field does not depend on position along the length, so A is false.
So the answer is (d) D only.

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Ampere's Law, Cylinders, Solenoid & Toroid question from JEE Main 2026 (28 Jan, Shift 2)

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