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 Sep 24th 2009, 09:19 AM #1 Banned   Join Date: Jul 2009 Posts: 66 help genii 1.According to Bohr model, magnetic field at the centre (at the nucleus) of a hydrogen atom due to the motion of electron in nth orbit is proportional to which given option (A) 1/n3 (B) 1/n5 (C) n5 (D) n3 plz explain also. i dont know to solve it.. I wonder magnetic field means intensity or its momenton or strength.. Despite these also i have no idea.
 Sep 25th 2009, 11:22 PM #2 Physics Team   Join Date: Feb 2009 Posts: 1,425 This is an interesting question. Think of the Hydrogen atom with the nucleus at the centre. Think of the orbit as a circular wire around it. The Bohr quantization condition gives us the angular momentum L $\displaystyle L\ =\ m\ \omega\ r^2\ =\ \frac{n\ h}{2\ \pi}$ . Thus it can be seen that omega is proportional to n . But $\displaystyle \omega\ =\ 2\ \pi \ f$ where f is the frequency. So f is proportional to n Thus, if we look at any point on the "orbit wire" , it is as though f electrons pass it each sec ( actually it is the same one !) Thus a charge of f . e coulombs passes any point on the wire per sec. e here is the charge of the electron. This corresponds to a current of $\displaystyle I\ =\ \frac{f\ e}{1}$ . Thus I is also proportional to n. Now look up the formula for the magnetic field at the centre of a current carrying loop and find what power of I it corresponds to. It should be the same for n.

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