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Saturday, 31 October

JEE Main 2022 · PhysicsMultiple choiceDiagram basedMediumMulti-step

JEE Main 26 July 2022, Shift 2, Physics Q46

Question 46 of 90 in this shift, Physics question 16 of 30, Section A.

Two concentric circular loops of radii r1r_1=30 cm and r2r_2=50 cm are placed in X-Y plane as shown in the figure. A current I=7AI = 7A is flowing through them in the direction as shown in figure. The net magnetic moment of this system of two circular loops is approximately :

The figure, in words

Two concentric circles with a common centre marked by a dot; radius r1 drawn in the inner circle and radius r2 drawn in the outer circle; each loop has a current arrow labelled I.
  1. (1)72k^ Am2\frac{7}{2}\hat{k}\ Am^{2}
  2. (2)−72k^ Am2-\frac{7}{2}\hat{k}\ Am^{2}Official answer
  3. (3)7 k^ Am27\ \hat{k}\ Am^{2}
  4. (4)−7 k^ Am2-7\ \hat{k}\ Am^{2}

Official answer

Option 2

NTA final key.

Chapter
Moving Charges and Magnetism
Topic
Magnetic Dipole Moment
Idea tested
Magnetic moment of a current loop

Same idea in other shifts

Asked 3× in all
  1. 29 Jul 2022, Shift 1 · Q58A wire of length 314 cm carrying current of 14 A is bent to form a circle. The magnetic moment of the coil is __________ A-m2\mathrm{m^2}.…MediumNumerical value
  2. 30 Jul 2022, Shift 2 · Q15A wire of length 8 m is bent to form a circular loop in y-z plane. A current of 0.5 A is flowing in anticlockwise direction in it , the…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. 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.