JEE Main 2021 (27 Aug, Shift 2) Physics Q11: A coaxial…

Question

A coaxial cable consists of an inner wire of radius ‘a’ surrounded by an outer shell of inner and outer radii ‘b’ and ‘c’ respectively. The inner wire carries an electric current

i_0

, which is distributed uniformly across cross-sectional area. The outer shell carries an equal current in opposite direction and distributed uniformly. What will be the ratio of the magnetic field at a distance

x

from the axis when (i)

x<

a and (ii) a

<x<

b ?

(1) $\frac{x^2}{a^2}$ Official answer
(2) $\frac{a^2}{x^2}$
(3) $\frac{x^2}{b^2-a^2}$
(4) $\frac{b^2-a^2}{x^2}$

Official answer

Option 1

NTA final key.

Accepted Answer

Option 1: $\frac{x^2}{a^2}$

Answer

$\frac{x^2}{a^2}$

Answer

$\frac{a^2}{x^2}$

Answer

$\frac{x^2}{b^2-a^2}$

Answer

$\frac{b^2-a^2}{x^2}$

JEE Main 27 August 2021, Shift 2, Physics Q11

Same idea in other shifts