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An electron in an atom is revolving around the nucleus in a circular orbit of radius 5.3 x 10-11 m, with a speed of 2 x 106 m/s. - Physics

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An electron in an atom is revolving around the nucleus in a circular orbit of a radius of 5.3 x 10-11 m, with a speed of 2 x 106 m/s. Find the resultant orbital magnetic moment and angular momentum of the electron. [e = 1.6 x 10-19 C, me= 9.1 x 10-31 kg]

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Solution 1

  1. Data: r = 5.3 × 10-11 m, v = 2 × 106 m/s,

e = 1.6 × 10-19 C, me = 9.1 × 10-31 kg

The orbital magnetic moment of the electron is

`"M"_0 = 1/2`evr

`= 1/2(1.6 xx 10^-19)(2xx10^6)(5.3 xx 10^-11)`

= 8.48 × 10-24 A.m2

The angular momentum of the electron is

L0 = mevr

= (9.1 × 10-31)(2 × 106)(5.3 × 10-11)

= 96.46 × 10-36 = 9.646 × 10-35 kg.m2/s

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Solution 2

Given:

r = `5.3 xx 10^-11` m,
v = `2 xx 10^6` ms-1
e = `1.6 xx 10^-19` C,
me = `9.1 xx 10^-31` kg

To find:

  1. Orbital magnetic moment (morb)
  2. Angular momentum of electron 

Formulae:

  1. morb = `"evr"/2`
  2. L = mvr 

Calculation: 

From formula (i),

morb = `(1.6 xx 10^-19 xx 2 xx 10^6 xx 5.3 xx 10^-11)/2`

= `1.6 xx 5.3 xx 10^-24`

= `8.48 xx 10^-24` Am2

From formula (ii),

L = `9.1 xx 10^-31 xx 2 xx 10^6 xx 5.3 xx 10^-11`

= `96.46 xx 10^-36`

∴ L ≈ `underline(9.646 xx 10^-35)` kgm2/s 

  1. Orbital magnetic moment is `8.48 xx 10^-24` Am2.
  2. Angular momentum of electron is `9.646 xx 10^-35` kgm2/s.   
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Origin of Magnetism in Materials
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Chapter 11: Magnetic Materials - Exercises [Page 264]

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