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Saturday, 31 October

JEE Main 2020 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 8 January 2020, Shift 1, Physics Q14

Question 14 of 75 in this shift, Physics question 14 of 25, Section A.

At time t = 0 magnetic field of 1000 Gauss is passing perpendicularly through the area defined by the closed loop shown in the figure. If the magnetic field reduces linearly to 500 Gauss, in the next 5 s, then induced EMF in the loop is :

The figure, in words

Closed loop: a 16 cm wide, 4 cm tall rectangle with a triangular notch cut in from each of the left and right ends (notch depth 2 cm, base along the full 4 cm side) so each end is a V shape.
  1. (1)28 μ\muV
  2. (2)36 μ\muV
  3. (3)48 μ\muV
  4. (4)56 μ\muVOfficial answer

Official answer

Option 4

NTA final key (Jan 2020).

Chapter
Electromagnetic Induction
Topic
Faraday's Law
Idea tested
Faraday's Law Magnitude

Same idea in other shifts

Asked 15× in all
  1. 5 Apr 2026, Shift 2 · Q50A circular loop of radius 20 cm and resistance 2 Ω\Omega is placed in a time varying magnetic field B⃗=(2t2+2t+3) T\vec{B}=(2t^2+2t+3)\ \mathrm{T}. At…EasyNumerical value
  2. 6 Apr 2026, Shift 2 · Q39A square loop of side 2 cm is placed in a time varying magnetic field with magnitude as B=0.4sin⁡(300t)B=0.4\sin(300t) Tesla. The normal to the plane…MediumSingle correct
  3. 29 Jan 2024, Shift 1 · Q58A square loop of side 10 cm and resistance 0.7 Ω0.7\,\Omega is placed vertically in east-west plane. A uniform magnetic field of 0.20 T0.20\ T is…EasyNumerical value
  4. 31 Jan 2024, Shift 2 · Q58The magnetic flux ϕ\phi (in weber) linked with a closed circuit of resistance 8 Ω8\ \Omega varies with time (in seconds) as…EasyNumerical value
  5. 11 Apr 2023, Shift 1 · Q53The magnetic field B crossing normally a square metallic plate of area 4 m2^2 is changing with time as shown in figure. The magnitude of…EasyNumerical valueHas a figure
  6. 12 Apr 2023, Shift 1 · Q58A conducting circular loop is placed in a uniform magnetic field of 0.4 T with its plane perpendicular to the field. Somehow, the radius…MediumNumerical value
  7. 25 Jul 2022, Shift 2 · Q60Magnetic flux (in weber) in a closed circuit of resistance 20 Ω\Omega varies with time t(s) as ϕ\phi = 8t2^{2} - 9t + 5. The magnitude…EasyNumerical value
  8. 26 Jul 2022, Shift 2 · Q58In a coil of resistance 8 Ω\Omega,the magnetic flux due to an external magnetic field varies with time as…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. 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.