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Homework Help: Right hand Rule - Check if i did this right

  1. Mar 2, 2005 #1
    Im having a really hard time with these...I have three different problems so here they are..

    Situation one: Particle moving up, field moving to the right. Thus the force has to be either into or out of the page so to speak because it has to be perpendicular. Through the right hand rule I got that the force would be out of the page, not sure if its right.

    Situation two: Field goes right, particle is going off at an angel A which appears to be about 210 degrees. Thus to be perpendicular the force is either going to be at 120 or 300 degrees. I used the right hand rule and got that it would be the 300 degrees.

    Situation Three: Field goes into the page (not down) and the angle this time goes up what seems 30 degrees. So to be perpendicular it either has to be 120 degrees or -60 (or 300) degrees. I got the 300 again.

    Really appreciate any help!
  2. jcsd
  3. Mar 2, 2005 #2
    This is what I get, but remember I'm pretty rusty at this:
    1 into page.
    2 is wrong. The vectors are coplanar with the page so the answer must be into or out of the page. (the force must always be perpendicular to the plane containing the other two vectors.)
    3. 120 .

    We are talking positive charges right? Negative will reverse the force.
  4. Mar 2, 2005 #3
    yes they are positive. Yeah I see what you mean on number 2, dont know why I thought that. Like I said i'm pretty bad at this so I'd trust yours over mine
  5. Mar 2, 2005 #4
    Don't know if this will help or just confuse you further, but I was taught the "right hand screw" rule. This works for the cross product of any two vectors. (Which is what we're doing here.)

    A x B (in e/m it is q(VxB) q is a scaler mulplier)

    The resultant vector is perpendicular to the plane containing A and B, it's direction given by the direction of advance of a right hand threaded screw turned the same way as when turning A into B through the _smaller_ angle between them.

    A x B = - B x A the direction reverses when you change the order, so remember thumb for V (or current i for a wire), index for B and second figure force.
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