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Saturday, 31 October

JEE Main 2022 · PhysicsMultiple choiceSingle correctMediumMulti-step

JEE Main 30 July 2022, Shift 2, Physics Q16

Question 16 of 90 in this shift, Physics question 16 of 30, Section A.

In the following loop, magnitude of the magnetic field produced at the centre (O) of the loop is : (Assume AB and CD are infinitely extended):

The figure, in words

Current I flows along a straight wire from A (left, extended to infinity) to B, then around a circular arc of radius R centred at O (going over the top and around the right side, about three-quarters of a circle) to C, then returns leftward along straight wire C to D (extended to infinity). Radii of length R from O to the arc and from O down to C are marked. Wires AB and CD are tangent to the circle at B and C respectively, on the same side.
  1. (1)μoI4πR(32π)\frac{\mu_o I}{4\pi R}\left(\frac{3}{2}\pi\right)
  2. (2)μoI2πR\frac{\mu_o I}{2\pi R}
  3. (3)μoI4πR(32π+1)\frac{\mu_o I}{4\pi R}\left(\frac{3}{2}\pi+1\right)Official answer
  4. (4)μoI4πR(32π−1)\frac{\mu_o I}{4\pi R}\left(\frac{3}{2}\pi-1\right)

Official answer

Option 3

NTA final key.

Chapter
Moving Charges and Magnetism
Topic
Biot-Savart Law
Idea tested
Field at center of circular arc

Same idea in other shifts

Asked 8× in all
  1. 3 Apr 2025, Shift 1 · Q48A loop ABCDA, carrying current I=12\mathrm{I} = 12 A, is placed in a plane, consists of two semi-circular segments of radius…MediumNumerical valueHas a figure
  2. 30 Jan 2024, Shift 1 · Q42Two insulated circular loop A and B of radius 'a' carrying a current of 'I' in the anti clockwise direction as shown in the figure. The…MediumDiagram basedHas a figure
  3. 31 Jan 2024, Shift 2 · Q57Two circular coils PP and QQ of 100 turns each have same radius of π\pi cm. The currents in PP and RR are 1A1A and 2A2A respectively.…MediumNumerical value
  4. 10 Apr 2023, Shift 2 · Q59A straight wire carrying a current of 14 A is bent into a semicircular arc of radius 2.2 cm as shown in the figure. The magnetic field…MediumNumerical valueHas a figure
  5. 26 Jul 2022, Shift 1 · Q39BXB_X and BYB_Y are the magnetic fields at the centre of two coils X and Y respectively each carrying equal current. If coil X has 200…EasySingle correct
  6. 3 Aug 2021, Shift 1 · Q13A current I enters a circular coil of radius R, branches into two parts at A and then recombines at B (as shown in figure). The resultant…MediumDiagram basedHas a figure
  7. 4 Sep 2020, Shift 1 · Q13A wire A, bent in the shape of an arc of a circle, carrying a current of 2 A and having radius 2 cm and another wire B, also bent in the…MediumDiagram basedHas a figure

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.