Magnetic field at the centre of the hydrogen atom due to motion of electron in $\mathrm{n}^{\text {th }}$…

Magnetic field at the centre of the hydrogen atom due to motion of electron in $\mathrm{n}^{\text {th }}$ orbit is proportional to
  1. $\mathrm{n}^4$
  2. $\mathrm{n}^{-3}$
  3. $\mathrm{n}^3$
  4. $\mathrm{n}^{-5}$

Solution

The radius of the $\mathrm{n}^{\text {th }}$ Bohr orbit is, $r_n \propto n^2$. The angular velocity of the electron, $\omega_n \propto \frac{1}{n^3}$ Also, current $I_n=\frac{q}{T_n}=\frac{q \omega_n}{2 \pi}$ $\begin{array}{ll} \therefore \quad & \mathrm{I}_{\mathrm{n}} \propto \omega_{\mathrm{n}} \propto \frac{1}{\mathrm{n}^3} \\ & \text { Now, } \mathrm{B}_{\mathrm{n}}=\frac{\mu_0 \mathrm{I}_{\mathrm{n}}}{2 \mathrm{r}_{\mathrm{n}}} \\ \therefore \quad & \mathrm{B}_{\mathrm{n}} \propto \frac{1}{\mathrm{n}^3} \times \frac{1}{\mathrm{n}^2} \\ \therefore \quad & \mathrm{B}_{\mathrm{n}} \propto \frac{1}{\mathrm{n}^5} \end{array}$

Asked in: MHT CET 2023 (14 May Shift 1)

Practice more Magnetic Fields due to Electric Current questions on Aicharya