JEE Main 2020 · PhysicsMultiple choiceDiagram basedHardMulti-step

JEE Main 8 January 2020, Shift 2, Physics Q12

Question 12 of 75 in this shift, Physics question 12 of 25, Section A.

A very long wire ABDMNDC is shown in figure carrying current I. AB and BC parts are straight, long and at right angle. At D wire forms a circular turn DMND of radius R. AB, BC parts are tangential to circular turn at N and D. Magnetic field at the centre of circle is :

The figure, in words

A vertical straight wire from A (bottom, arrow pointing up) to B, and a horizontal straight wire from near B/D to C (arrow pointing right, dotted continuation beyond C); a right-angle mark at B. A circle with a dot at its centre sits above the horizontal wire, touching the vertical wire at N (left of circle) and the horizontal wire at D (bottom of circle); M is marked at the top of the circle with an arrowhead on the circle.

(1) $\frac{\mu_0 I}{2\pi R}\left(\pi+\frac{1}{\sqrt{2}}\right)$ Official answer
(2) $\frac{\mu_0 I}{2\pi R}\left(\pi-\frac{1}{\sqrt{2}}\right)$
(3) $\frac{\mu_0 I}{2R}$
(4) $\frac{\mu_0 I}{2\pi R}(\pi+1)$

Official answer

Option 1

NTA final key (Jan 2020).

Chapter: Moving Charges and Magnetism
Topic: Biot-Savart Law
Idea tested: Superposition of magnetic fields

JEE Main 8 January 2020, Shift 2, Physics Q12

Same idea in other shifts