Calculating Angular as a Function of Proton Movement in Magnetic Field

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The discussion focuses on deriving a formula for protons moving in a magnetic field, specifically looking to express momentum (p) as a function of magnetic field strength (B) and radius (r). The initial formula presented is p = qrB, where q is the charge of the proton. The user seeks clarification on the correct units for B and q to ensure accurate calculations, emphasizing the importance of converting GeV to Joules and using SI units. They provide a revised formula that relates momentum in GeV/c to the magnetic field and radius, concluding with a practical example of a 1 GeV particle in a 3T field. The conversation highlights the complexities of unit conversion and the relationships between physical quantities in magnetic fields.
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?

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

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...
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}]}
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<br />

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!
 
I do not have a good working knowledge of physics yet. I tried to piece this together but after researching this, I couldn’t figure out the correct laws of physics to combine to develop a formula to answer this question. Ex. 1 - A moving object impacts a static object at a constant velocity. Ex. 2 - A moving object impacts a static object at the same velocity but is accelerating at the moment of impact. Assuming the mass of the objects is the same and the velocity at the moment of impact...

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