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MHT CET 2021 (22 Sep, Shift 1) · Biot-Savart Law & Circular Coils

Biot-Savart Law & Circular Coils question from MHT CET 2021 (22 Sep, Shift 1)

Q81MHT CET 2021 · 22 SEP · SHIFT 1Difficult

Biot-Savart Law & Circular Coils

Assuming the atom is in the ground state, the expression for the magnetic field at a point nucleus in hydrogen atom due to circular motion of electron is [μ0=\mu_0 = permeability of free space, m=m = mass of electron, ϵ0=\epsilon_0 = permittivity of free space, h=h = Planck's constant ]

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Answer: (a)

  1. Bohr ground state: r=ϵ0h2πme2r = \dfrac{\epsilon_0 h^2}{\pi m e^2}, v=e22ϵ0hv = \dfrac{e^2}{2\epsilon_0 h}.
  2. Current I=ev2πrI = \dfrac{ev}{2\pi r}, so B=μ0I2r=μ0ev4πr2B = \dfrac{\mu_0 I}{2r} = \dfrac{\mu_0 e v}{4\pi r^2}.
  3. B=μ0e4π⋅e22ϵ0h⋅π2m2e4ϵ02h4=μ0e7πm28ϵ03h5B = \dfrac{\mu_0 e}{4\pi}\cdot\dfrac{e^2}{2\epsilon_0 h}\cdot\dfrac{\pi^2 m^2 e^4}{\epsilon_0^2 h^4} = \dfrac{\mu_0 e^7 \pi m^2}{8\epsilon_0^3 h^5}
  4. So the answer is (a).
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