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Magnetism - Is there a magnetic force on the lectron

  1. Jul 16, 2010 #1
    1. The problem statement, all variables and given/known data
    It is a multiple choice question. The picture shows two bar magnet attracting each other. A charge is placed in the middle of the distance between the two magnets.

    [S-Magnet-N] >>>> (-C) >>>> [S-Magnet-N]

    >>> = direction of field lines. (-C) =negative

    There is no magnetic force on the electron when it moves : ?
    A ) towards the right side of the page
    B ) towards the top of the page
    C ) into the page
    D ) out of the page
    Firstly, i have no idea how do they define a "page". Secondly, shouldn't the electron move along the magnetic field lines ? Last but not least ( i got a lot of problems with physics ) , does this requires any left hand rule or right hand rule ?

    2. Relevant equations

    NIL

    3. The attempt at a solution

    I felt that the answer is towards the top of the page.


    I thank you in advance for the time taken to help me solve this relatively simple question...
    Thanks and have a nice day ~
     
  2. jcsd
  3. Jul 16, 2010 #2

    kuruman

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    Re: Magnetism

    Replace "page" with "screen" and you will be OK.

    Why should the electron move along the magnetic field lines?

    Partial answer: "Because if it didn't ...." (Yes, use the right hand rule)
     
  4. Jul 16, 2010 #3
    Re: Magnetism

    What is a screen ? :( Is it possible to have a 3-D representation drawn out ?
    Regarding using right hand rule, the magnetic field lines point where? Current is which direction ? >>>> or <<<< ... I think since this is an electron... current is opposite direction of where electron is moving... but is the electron moving ?! Sorry, i'm a bit weak
     
  5. Jul 16, 2010 #4

    kuruman

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    Re: Magnetism

    A screen is what you are staring at as you read this message.
    The magnetic field lines point as you have drawn them >>>>> left to right.
    There is no current here. Just the magnetic field lines and the electron that does not experience a force although it is moving. Ask yourself the following questions.

    1. What is the expression that gives the force on a moving electron in a magnetic field?
    2. Under what circumstances is this force zero?
     
  6. Jul 16, 2010 #5
    Re: Magnetism

    My knowledge of this subject is too weak that i needed to search online regarding your questions :( Beside, my level of education doesn't teach about equation to calculate force in a magnetic field... I stumbled upon this website and i think it solved my problem.http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfor.html#c2
    The answer is when the charge is moving parallel to the magnetic field where the force is zero. Thanks.

    One question : Does the sign of the charge matters in which direction it moves? i.e negative and positive move in the same direction due to magnetic field lines?
     
  7. Jul 16, 2010 #6

    kuruman

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    Re: Magnetism

    The sign of the charge determines the direction of the force on the charged particle. Of course if the force is zero as in this case, the sign does not matter. Any charge moving parallel to the magnetic field will experience zero force.
     
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