Angular momentum of this classical electron?

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SUMMARY

The discussion focuses on calculating the quantum number L that corresponds to the angular momentum of a classical electron moving in a circular path with a radius of 0.5 mm and a velocity of 20 m/s. The classical angular momentum is computed using the formula L = r * p, resulting in L = 0.010 kg·m²/s. To find the quantized angular momentum, the discussion references Bohr's model, specifically the formula L = nħ/2π, where n is the principal quantum number. The lowest value for n is 1, which provides a basis for comparison with the classical angular momentum.

PREREQUISITES
  • Understanding of classical mechanics, specifically angular momentum calculations.
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  • Knowledge of the reduced Planck constant (ħ) and its application in quantum formulas.
  • Ability to manipulate and analyze equations involving quantum numbers.
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  • Research the implications of Bohr's model on angular momentum quantization.
  • Learn how to calculate angular momentum using L = nħ/2π for various quantum states.
  • Explore the relationship between classical and quantum angular momentum in different systems.
  • Investigate the significance of the azimuthal quantum number l and its relationship to principal quantum number n.
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Students and educators in physics, particularly those studying classical mechanics and quantum mechanics, as well as anyone interested in the transition from classical to quantum models of particle behavior.

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Homework Statement


a classical electron moves in a circle of radius 0.5mm with velocity 20ms-1
what is the value of the quantum number L which gives a quantised angular momentum close to the angular momentum of this classical electron?


Homework Equations



L=r * p

The Attempt at a Solution



L=r*p
500e-6 * 20=0.010
 
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You need to throw in the equation for quantum angular momentum.
 
is it L=\sqrt{l(l+1)hbar}
 
is it possible to find the value of the quantum number "l" (azimuthal quantum number)?
 
Check the dimensions in that formula.
 
do i have to presume that n=1 before i continue the calculation, because there is no mention of principal quantum number in the question?
 
The description says "classical electron". So I guess you should use Bohr's model here. What is the angular momentum in Bohr's model?
 
the lowest value for n is 1, this gives the smallest orbital radius 0.0529nm(bohr radius)
L=r*p=mvr m=9.1e-31, v=20m/s r=0.5nm
mvr=nhbar

L=n h/2pi=nhbar
 
I think you should use the latter formula to determine n that gives the closest match of L to that of the classical electron.
 
  • #10
can you explain that again please
 
  • #11
You can compute the angular momentum from the radius and velocity given.

You have the formula for the angular momentum in Bohr's model. What n gives the closest fit between the two?

You could also consider the other formula, involving the square root of l(l + 1). For large n, and correspondingly large l, what can be said about the results given by these two equations?
 

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