Learn

Friday, 9 October

JEE Main 2022 · PhysicsMultiple choiceSingle correctEasyCalculation

JEE Main 24 June 2022, Shift 1, Physics Q49

Question 49 of 90 in this shift, Physics question 19 of 30, Section A.

The magnetic field at the centre of a circular coil of radius r, due to current I flowing through it, is B. The magnetic field at a point along the axis at a distance r2\frac{r}{2} from the centre is :
  1. (1)B/2B/2
  2. (2)2B2B
  3. (3)(25)3B\left(\frac{2}{\sqrt{5}}\right)^3 BOfficial answer
  4. (4)(23)3B\left(\frac{2}{\sqrt{3}}\right)^3 B

Official answer

Option 3

NTA final key (2022 Session 1).

Chapter
Moving Charges and Magnetism
Topic
Biot-Savart Law
Idea tested
Ratio of Axial to Central Magnetic Field

Same idea in other shifts

Asked 3× in all
  1. 2 Apr 2025, Shift 1 · Q38Let B1B_1 be the magnitude of magnetic field at center of a circular coil of radius R carrying current I. Let B2B_2 be the magnitude of…EasySingle correct
  2. 8 Apr 2023, Shift 2 · Q59The ratio of magnetic field at the centre of a current carrying coil of radius rr to the magnetic field at distance rr from the centre…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. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.