JEE Main · 2023 · 29 Jan 2023 · Shift 1 · Magnetic Effects of Current

A single current carrying loop of wire carrying current I flowing in anticlockwise direction seen from +ve

z

direction and lying in xy plane in shown in figure. The plot of

\hat{j}

component of magnetic field (By) at a distance 'a' (less than radius of the coil) and on

y z

plane vs

z

coordinate look like

Answer: (C)

Solution

In the plane of the loop the field is purely axial, so the

y

-component

B_{y} (0, a, z)

vanishes at

z = 0

. Above the plane the spreading field lines give

B_{y}

one sign, and below the plane the mirror symmetry of the loop reverses it, so

B_{y} (- z) = - B_{y} (z)

. The component is therefore an odd function that passes through zero at the centre, dips to one side for

z < 0

and rises to a peak for

z > 0

before decaying. The plot with this odd, antisymmetric shape is the correct one.

JEE Main · 2023 · 29 Jan 2023 · Shift 1 · Single correct option