1. How to calculate the momentum of an electron ?
Measuring the radius of curvature in a magnetic field …
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Dora Wagner & Miguel Vieira HST 2001

2. They go on spirals if they are also loosing energy
If electrons are entering a magnetic field, they are forced to go on a circle.
They go on spirals if they are also
loosing energy
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Dora Wagner & Miguel Vieira HST 2001

3. The Lorentz-law helps to describe this behaviour :
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Dora Wagner & Miguel Vieira HST 2001

4. Dora Wagner & Miguel Vieira HST 2001
goes into the page !
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Dora Wagner & Miguel Vieira HST 2001

5. Dora Wagner & Miguel Vieira HST 2001
The Lorentz-force is the centripetal force, which pulls the electrons to the centre :
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Dora Wagner & Miguel Vieira HST 2001

6. Look at this sketch… …click it !
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Dora Wagner & Miguel Vieira HST 2001

7. Dora Wagner & Miguel Vieira HST 2001
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Dora Wagner & Miguel Vieira HST 2001

8. How to measure the radius ?
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Dora Wagner & Miguel Vieira HST 2001

9. Dora Wagner & Miguel Vieira HST 2001
If we know the radius r …
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Dora Wagner & Miguel Vieira HST 2001

10. … and if we know the strength of the magnetic field B…
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Dora Wagner & Miguel Vieira HST 2001

11. … we are able to calculate the momentum :
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Dora Wagner & Miguel Vieira HST 2001

12. Dora Wagner & Miguel Vieira HST 2001
Try it !
What to measure,
what to know
Scale 1 : 6.4
For more information
click here
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Dora Wagner & Miguel Vieira HST 2001

13. Dora Wagner & Miguel Vieira HST 2001
In the Fermilab where this picture was taken, the magnetic field was :
B = 3 Tesla
The charge of the observed electron is :
e = 1.6x10-19 Coulomb
07/17/2001
Dora Wagner & Miguel Vieira HST 2001

14. Dora Wagner & Miguel Vieira HST 2001
Are you able to use the Pythagoras theorem to calculate the radius r from L and D ?
BACK
07/17/2001
Dora Wagner & Miguel Vieira HST 2001

15. A photon traveled between the two marked points
A photon traveled between the two marked points. The traveled distance was, in the real experiment,
11.5 cm!
If you want to know more,click-me
07/17/2001
Dora Wagner & Miguel Vieira HST 2001