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Friday, 9 October

JEE Main 2025 · PhysicsNumerical answerNumerical valueMediumMulti-step

JEE Main 3 April 2025, Shift 1, Physics Q48

Question 48 of 75 in this shift, Physics question 23 of 25, Section B.

A loop ABCDA, carrying current I=12\mathrm{I} = 12 A, is placed in a plane, consists of two semi-circular segments of radius R1=6π\mathrm{R_1} = 6\pi m and R2=4π\mathrm{R_2} = 4\pi m. The magnitude of the resultant magnetic field at center O is k×10−7k\times10^{-7} T. The value of k is ________. (Given μ0=4π×10−7 Tm A−1\mu_0 = 4\pi \times 10^{-7}\ \mathrm{Tm\,A^{-1}})

The figure, in words

Points A, B, O, C, D lie on a horizontal line in that order; a large semicircle of radius R_1 runs from A to D above the line and a small semicircle of radius R_2 from B to C above the line, both centred at O; current I flows along A to B, around the small arc, C to D and back along the large arc.

Official answer

1

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 2× in all
  1. 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

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 42 of the 174 JEE Main shifts held from 2017 to 2026.