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Friday, 9 October

JEE Main 2020 · PhysicsMultiple choiceSingle correctHardMulti-step

JEE Main 6 September 2020, Shift 2, Physics Q15

Question 15 of 75 in this shift, Physics question 15 of 25.

A square loop of side 2a and carrying current I is kept in xzxz plane with its centre at origin. A long wire carrying the same current I is placed parallel to zz-axis and passing through point (0,b,0)(0, b, 0), (b≫a)(b \gg a). The magnitude of torque on the loop about zz-axis will be :
  1. (1)2μ0I2a2πb\frac{2\mu_0 I^2 a^2}{\pi b}
  2. (2)2μ0I2a2bπ(a2+b2)\frac{2\mu_0 I^2 a^2 b}{\pi(a^2+b^2)}Official answer
  3. (3)μ0I2a2b2π(a2+b2)\frac{\mu_0 I^2 a^2 b}{2\pi(a^2+b^2)}
  4. (4)μ0I2a22πb\frac{\mu_0 I^2 a^2}{2\pi b}

Official answer

Option 2

NTA final key (Sep 2020).

Chapter
Moving Charges and Magnetism
Topic
Magnetic Dipole Moment
Idea tested
Torque from a Straight Wire Field

Same topic in other shifts

All Magnetic Dipole Moment questions
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  3. 4 Apr 2026, Shift 2 · Q49A circular coil of radius 2 cm and 125 turns carries a current of 1 A. The coil is placed in a uniform magnetic field of magnitude 0.4 T.…EasyNumerical value
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  5. 3 Apr 2025, Shift 2 · Q36A magnetic dipole experiences a torque of 80380\sqrt{3} N m when placed in uniform magnetic field in such a way that dipole moment makes…EasySingle correct
  6. 6 Apr 2024, Shift 2 · Q58A coil having 100 turns, area of 5×10−3 m25\times10^{-3}\ \mathrm{m^2}, carrying current of 1 mA is placed in uniform magnetic field of 0.20 T…EasyNumerical 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.