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JEE Main 2020 (7 Jan, Shift 1) · Magnetic Flux & Faraday's Law

Magnetic Flux & Faraday's Law question from JEE Main 2020 (7 Jan, Shift 1)

Q72JEE Main 2020 · 7 JAN · SHIFT 1Difficult

Magnetic Flux & Faraday's Law

A loop ABCDEFA of straight edges has six corner points A(0, 0, 0), B(5, 0, 0), C(5, 5, 0), D (0, 5, 0), E(0, 5, 5) and F(0, 0, 5). The magnetic field in this region is B⃗=(3i^+4k^)T\vec{B} = \left(3\hat{i}+4\hat{k}\right)T. The quantity of flux through the loop ABCDEFA (in Wb) is _______.

Numerical answer type. Work it out, then open the answer.

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Answer: 175

  1. Split the loop into two squares: ABCD in the z=0z=0 plane and ADEF in the x=0x=0 plane, each of area 2525 m2^2.
  2. Going A→B→C→D, the area vector of ABCD is 25k^25\hat{k}; going D→E→F→A, the area vector of ADEF is 25i^25\hat{i}.
  3. A⃗=(25i^+25k^)\vec{A} = (25\hat{i} + 25\hat{k}) m2^2.
  4. ϕ=B⃗⋅A⃗=3(25)+4(25)=175\phi = \vec{B}\cdot\vec{A} = 3(25) + 4(25) = 175 Wb.
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