Learn

Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 31 August 2021, Shift 2, Physics Q17

Question 17 of 90 in this shift, Physics question 17 of 30, Section A.

A current of 1.5 A is flowing through a triangle, of side 9 cm each. The magnetic field at the centroid of the triangle is : (Assume that the current is flowing in the clockwise direction.)
  1. (1)3×10−53\times10^{-5} T, inside the plane of triangleOfficial answer
  2. (2)3×10−73\times10^{-7} T, outside the plane of triangle
  3. (3)23×10−52\sqrt{3}\times10^{-5} T, inside the plane of triangle
  4. (4)23×10−72\sqrt{3}\times10^{-7} T, outside the plane of triangle

Official answer

Option 1

NTA final key.

Chapter
Moving Charges and Magnetism
Topic
Biot-Savart Law
Idea tested
Field at Center of Regular Polygon

Same idea in other shifts

Asked 5× in all
  1. 8 Apr 2025, Shift 2 · Q39Figure shows a current carrying square loop ABCD of edge length is 'a' lying in a plane. If the resistance of the ABC part is r and that…HardDiagram basedHas a figure
  2. 1 Feb 2024, Shift 1 · Q57A regular polygon of 6 sides is formed by bending a wire of length 4π4\pi meter. If an electric current of 4π34\pi\sqrt{3} A is flowing…MediumNumerical value
  3. 30 Jan 2024, Shift 2 · Q57The current of 5A flows in a square loop of sides 1 m1\ m is placed in air. The magnetic field at the centre of the loop is…EasyNumerical value
  4. 3 Sep 2020, Shift 1 · Q13Magnitude of magnetic field (in SI units) at the centre of a hexagonal shape coil of side 10 cm, 50 turns and carrying current I (Ampere)…MediumSingle correct

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. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.