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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumMulti-step

JEE Main 18 March 2021, Shift 1, Physics Q3

Question 3 of 90 in this shift, Physics question 3 of 30, Section A.

Four identical long solenoids A, B, C and D are connected to each other as shown in the figure. If the magnetic field at the center of A is 3 T, the field at the center of C would be : (Assume that the magnetic field is confined with in the volume of respective solenoid).

The figure, in words

Solenoid A in series with input current i; then three parallel solenoids B (top), C (middle), D (bottom) joined at both ends, output on the right.
  1. (1)1 TOfficial answer
  2. (2)9 T
  3. (3)6 T
  4. (4)12 T

Official answer

Option 1

NTA final key.

Chapter
Moving Charges and Magnetism
Topic
Ampere's Circuital Law
Idea tested
Ideal Infinite Solenoid

Same idea in other shifts

Asked 5× in all
  1. 5 Apr 2024, Shift 2 · Q57A solenoid of length 0.5 m has a radius of 1 cm and is made up of 'm' number of turns. It carries a current of 5 A. If the magnitude of…EasyNumerical value
  2. 8 Apr 2023, Shift 1 · Q58The magnetic intensity at the center of a long current carrying solenoid is found to be 1.6×103 Am−11.6\times10^3\ \mathrm{Am^{-1}}. If the number…EasyNumerical value
  3. 25 Jun 2022, Shift 2 · Q41A long solenoid carrying a current produces a magnetic field BB along its axis. If the current is doubled and the number of turns per cm…EasySingle correct
  4. 17 Mar 2021, Shift 1 · Q4A solenoid of 1000 turns per metre has a core with relative permeability 500. Insulated windings of the solenoid carry an electric current…EasySingle 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. 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.