Radius of hellical chain (radius of path of electron)?

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Homework Help Overview

The discussion revolves around calculating the radius of the path of an electron in a helical motion, with a specific focus on the components of velocity and the application of relevant equations. The original poster expresses a discrepancy between their calculated radius and the expected answer.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the necessity of using the perpendicular component of velocity in the calculations. The original poster questions their own calculations and seeks clarification on the use of angles in the formula.

Discussion Status

Some guidance has been offered regarding the use of the angle in the calculations, and participants are exploring the implications of this on the results. There is an ongoing examination of the original poster's approach and potential errors in their reasoning.

Contextual Notes

The original poster's calculations yield a different result than expected, leading to questions about the assumptions made in their approach. The discussion includes references to specific values and angles used in the calculations.

delsoo
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Homework Statement



here's the question, is my concept correct? the ans is 9.86 cm, but my ans is 13 cm, can anyone tell me which part is wrong?

Homework Equations





The Attempt at a Solution

 

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For your formula, you have to take the perpendicular component of the velocity only.
 
mfb said:
For your formula, you have to take the perpendicular component of the velocity only.

perpendicular velocity is v sin tetha, so i sub all the values to the working above, i would get r=(mv)/(Bq sin 60) , where m=9.1x10^-31 , v= 4.0x10^7 ms^-1 B=2.0x10^-3 T , q=1.6X10^-9C , i would get 0.13m but not 9.86 cm... what's wrong with my working?
 
At one side you did use the angle, but I think at the other side you did not.
 
mfb said:
At one side you did use the angle, but I think at the other side you did not.

what do u mean? can you expalin more detail?
 

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