Rankers Physics

Ampere's Circuital Law: Practice Problem & Solution

From Ampere's circuital law for a long straight wire of circular cross section carrying a steady current, the variation of magnetic field in the inside and outside region of the wire is: (2022)
a linearly decreasing function of distance upto the boundary of the wire and then a linearly increasing one for the outside region.
uniform and remains constant for both the regions.
a linearly increasing function of distance upto the boundary of the wire and then decreasing outside region.
a linearly increasing function of distance $r$ upto the boundary of the wire $1/r$ dependence for the outside region.

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Ampere's Circuital Law. Understanding the underlying formula is key to arriving at the correct answer below:

Inside a uniform cylindrical wire, the magnetic field is directly proportional to the radius ($B \propto r$), increasing linearly. Outside the wire, the magnetic field is inversely proportional to the distance ($B \propto 1/r$). Therefore, option D is the correct choice.

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