1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Lorentz force

  1. Feb 3, 2012 #1

    I have a particle moving in a static electromagnetic field in which E and B have the following components:
    E=(Ex, 0, 0)
    B=(-Bx, 0, 0)
    and both depend on z, namely Ex(z) and Bx(z).
    The particle is moving along z with constant velocity v=(0, 0, vz).

    If I want to express Lorentz force as a function of z, is it correct to write:

    F(z)=q [(E *cross (1/v)) *cross (1/v) + B *cross (1/v)]?

    I get this equation considering F=q(E+v *cross B) as a system of 6 differential equations:

    dvx/dt= q*Ex/m

    and expressing them as a function of z
  2. jcsd
  3. Feb 3, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi 1Keenan! :smile:
    No. :confused:
    (write "x" not "*cross" :wink:)

    Where do the 1/v come from? :confused:
  4. Feb 3, 2012 #3
    My particle is moving along z and v=[0,0,vz]
    of course it will have a displacement along x and y but the intial velocity has only one component.
    Could you please explain your point?

    it comes from the differential equation:

    I change the variable t in z... it is a bit of algebra I can write you everything if you want so you can double check my manipulation.
  5. Feb 3, 2012 #4


    User Avatar
    Science Advisor
    Homework Helper

    but that doesn't mean that dx/dt = dy/dt = 0, not even initially :redface:
    i still don't get it :redface:
  6. Feb 3, 2012 #5
    What does it mean? :confused:

    How do you write it down?
    I don't understand what is tricky for you....
  7. Feb 3, 2012 #6
    I was thinking, and actually I'm doing something stupid, but I'm really interested in expressing those differential equation as function of z and I'm lost in papers full of my wrong formulas...
    at the moment I'm not able to calculate 1+1.... :(
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook