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MHT CET 2026 (12 May, Shift 2) · Bohr Model: Orbits, Speed & Angular Momentum

Bohr Model: Orbits, Speed & Angular Momentum question from MHT CET 2026 (12 May, Shift 2)

Q24MHT CET 2026 · 12 MAY · SHIFT 2Medium

Bohr Model: Orbits, Speed & Angular Momentum

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, ϵ0\epsilon_0 = permittivity of free space, mm = mass of electron, ee = electronic charge)

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Answer: (b)

  1. B=μ0I2rB = \frac{\mu_0 I}{2r} with I=ev2πrI = \frac{ev}{2\pi r}, so B=μ0ev4πr2B = \frac{\mu_0 e v}{4\pi r^2}
  2. Ground state: v=e22ε0hv = \frac{e^2}{2\varepsilon_0 h}, r=ε0h2πme2r = \frac{\varepsilon_0 h^2}{\pi m e^2}
  3. B=μ0e4π⋅e22ε0h⋅π2m2e4ε02h4B = \frac{\mu_0 e}{4\pi}\cdot\frac{e^2}{2\varepsilon_0 h}\cdot\frac{\pi^2 m^2 e^4}{\varepsilon_0^2 h^4}
  4. B=μ0e7πm28ε03h5B = \frac{\mu_0 e^7 \pi m^2}{8\varepsilon_0^3 h^5}, so the answer is (b).
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