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JEE Main 2026 (2 Apr, Shift 1) · Magnetic Flux & Faraday's Law

Magnetic Flux & Faraday's Law question from JEE Main 2026 (2 Apr, Shift 1)

Q22JEE Main 2026 · 2 APR · SHIFT 1Difficult

Magnetic Flux & Faraday's Law

When a coil is placed in a time dependent magnetic field the power dissipated in it is PP. The number of turns, area of the coil and radius of the coil wire are N, AN,\ A and rr respectively. For a second coil number of turns, area of the coil and radius of the coil wire are 2N, 2A2N,\ 2A and 3r3r respectively. When the first coil is replaced with second coil the power dissipated in it is 2 αP\sqrt{2}\,\alpha P. The value of α\alpha is ______.

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Answer: (a)

  1. e∝NAe \propto NA; wire length ∝NA\propto N\sqrt{A}, so R∝NAr2R \propto \dfrac{N\sqrt{A}}{r^2}.
  2. P=e2R∝N2A2r2NA=NA3/2r2P = \dfrac{e^2}{R} \propto \dfrac{N^2A^2 r^2}{N\sqrt{A}} = N A^{3/2} r^2.
  3. P′P=2×23/2×32=18×22=362\dfrac{P'}{P} = 2 \times 2^{3/2} \times 3^2 = 18\times 2\sqrt{2} = 36\sqrt{2}.
  4. 2 α=362⇒α=36\sqrt{2}\,\alpha = 36\sqrt{2} \Rightarrow \alpha = 36. So the answer is (a) 36.
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