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Friday, 9 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 topic in other shifts

All Ampere's Circuital Law questions
  1. 4 Apr 2026, Shift 2 · Q39A solenoid has a core made of material with relative permeability 400. The magnetic field produced in the interior of solenoid is 1.0 T.…EasySingle correct
  2. 6 Apr 2023, Shift 1 · Q40A long straight wire of circular cross-section (radius a) is carrying steady current I. The current I is uniformly distributed across this…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 42 of the 174 JEE Main shifts held from 2017 to 2026.