Calculating Angular as a Function of Proton Movement in Magnetic Field

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Discussion Overview

The discussion centers around deriving a formula related to protons moving in a magnetic field, specifically calculating momentum (p) as a function of magnetic field strength (B) and radius (r). Participants explore unit conversions and the relationships between these variables in the context of particle physics.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant derived a formula p = qrB and expressed a desire to relate momentum to magnetic field strength and radius.
  • Another participant suggested converting all units to SI to avoid confusion, recommending specific conversions for GeV to Joules and charge to Coulombs.
  • A participant attempted to express momentum in terms of radius and magnetic field, showing a calculation that included constants and units but later acknowledged confusion in their approach.
  • Further clarification was provided on the relationship between momentum, charge, radius, and magnetic field strength, with a specific example illustrating how a 1 GeV particle behaves in a magnetic field.
  • Expressions of gratitude were made for the assistance provided in the discussion.

Areas of Agreement / Disagreement

Participants generally agree on the need for unit conversions and the relationships between the variables involved, but there is no consensus on the final form of the equations or the specific values to use in calculations.

Contextual Notes

Some participants noted confusion regarding units and the correct form of the equations, indicating that assumptions about the relationships between variables may need further clarification.

Who May Find This Useful

This discussion may be useful for students or individuals interested in particle physics, particularly those working on problems involving protons in magnetic fields and the associated calculations of momentum and charge.

liquidFuzz
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I just derived a little formula of protons moving in a magnetic field. With the symetry etc I have I get this:

p = qrB

Now I want to calculate the angular as a function like this:

p = constant * B

Where p is Gev/C, r is in meters.

I don't know what numbers or better what form B and q should have to get all numbers right. Anyone care to shine some light on this..?

Edit, my field is 1.74T r in meters.
 
Last edited:
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Rule of thumb for such cases - if you are confused by units, convert everything to SI.
You need to convert GeV into Joules, and express proton charge in Coulombs and speed of light in m/s. Google for those values!
 
Mhmm...

Something like this?

[tex]\displaystyle p = 1.602 * 10^{-19} * 5.609*10^{35} r * 1.74 =1.56*r \frac{eV}{c^2} \frac{m}{s}[/tex]

Edit, I see that I've confused more than the units. I wanted to compute it like this p = constant * r
 
Last edited:
OK, I see I must do it for you...
[tex]p_{[{\rm kg\,m\,s^{-1}}]} = q_{[{\rm Q}]}r_{[{\rm m}]}B_{[{\rm T}]}<br /> = 1.602\cdot 10^{-19}{\rm C}\,r_{[{\rm m}]}B_{[{\rm T}]}[/tex]
[tex]p_{[{\rm GeV}/c]} = \frac{p_{[{\rm kg\,m\,s^{-1}}]}\cdot 3\cdot 10^8{\rm m\,s^{-1}}}<br /> {1.602\cdot 10^{-10}{\rm kg\,m^2\,s^{-2}\,GeV^{-1}}} =<br /> \frac{1.602\cdot 10^{-19}{\rm C}\,r_{[{\rm m}]}B_{[{\rm T}]} \cdot 3\cdot 10^8{\rm m\,s^{-1}}}<br /> {1.602\cdot 10^{-10}{\rm kg\,m^2\,s^{-2}\,GeV^{-1}}} = <br /> 0.3\, \frac{{\rm GeV}}{c}{\rm\,\,m^{-1}\,T^{-1}}\cdot r \cdot B[/tex]

Or - in other words - easier to remember and imagine - 1GeV particle makes circles of 1m radius in 3T field.
 
Thanks for taking the time to help me!
 

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