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JEE Main 2022 (25 Jul, Shift 1) · Mutual Inductance

Mutual Inductance question from JEE Main 2022 (25 Jul, Shift 1)

Q48JEE Main 2022 · 25 JUL · SHIFT 1Medium

Mutual Inductance

A small square loop of wire of side ll is placed inside a large square loop of wire L(L≫l)L (L \gg l). Both loops are coplanar and their centres coincide at point OO as shown in figure. The mutual inductance of the system is:

Figure

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Answer: (c)

  1. Field at the centre of the big square: B=22 μ0IπLB = \frac{2\sqrt{2}\,\mu_0 I}{\pi L} (four sides, each μ0I4π(L/2)⋅2sin⁡45∘\frac{\mu_0 I}{4\pi (L/2)} \cdot 2\sin 45^\circ).
  2. Since l≪Ll \ll L, flux through the small square: ϕ=Bl2=22 μ0Il2πL\phi = B l^2 = \frac{2\sqrt{2}\,\mu_0 I l^2}{\pi L}
  3. M=ϕ/I=22 μ0l2πLM = \phi / I = \frac{2\sqrt{2}\,\mu_0 l^2}{\pi L}
  4. So the answer is (c).
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