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Homework Help: Electromagntic Question !

  1. Dec 8, 2009 #1
    I got this question on an Assigment, and ..man, am having really hard time with it

    Here is how it start :

    "A student used the apparatus shown below to measure the radius of the curvature of the path of electrons as they pass through a magnetic field that is perpendicular to their path. This experimental design has the voltage as the manipulated variable, the speed calculated from the voltage, and the radius as the responding variable.

    Accelerating Potential Difference (V) |Speed (106 m/s)| Radius (10-2 m)
    20.0 | 2.65 | 7.2
    40.0 | 3.75 | 9.1
    60.0 | 4.59 | 11.0
    80.0 | 5.30 | 12.8
    100.0 | 5.93 | 14.1
    120.0 | 6.49 | 16.3

    A. Plot the graph of radius as a function of speed, and construct a best-fit line.

    B. Using the slope or other appropriate averaging technique, determine the strength of the magnetic field.

    C. Derive the equation that would allow you to calculate the speed of the electrons from the accelerating potential.

    Am so sorry for the lack of my Solutions, but am really having troubles with this unit (Electromagntic)
    if anyone know a tutorial or a website that explained this unit in easy and simple way, please include it in your answer... i need all the help i can get for this unit.

    any help is really appreciated guys, thank you
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Dec 8, 2009 #2


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    Homework Helper

    "Easy and simple" varies from person to person. If you're really having trouble with the entire subject of electromagnetism, I think you may need more personalized help than we can offer here.

    As for this assignment specifically: whenever you have a charged particle that moves in a magnetic field, without any other forces, it will move in a circle. This is called cyclotron motion. What have you learned about cyclotron motion? (Go back and look it up in your textbook/notes/references if you need to)
  4. Dec 10, 2009 #3
    I know Equations that may help us Calculate the magnetic strength
    Fm = (mv2/R)
    Fm= I L B

    But I don’t know (and didn’t find anything in my notes) about how to get the Magnetic Field strength from a Radius Vs Time graph
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