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!

Homework Help: Does a stationary electron in magnetic field experience Lorentz force?

  1. Apr 21, 2012 #1
    1. The problem statement, all variables and given/known data

    If an electron is stationary in a magnetic field, will it experience a Lorentz force?

    2. Relevant equations

    3. The attempt at a solution

    The total vector force (Lorentz force - F) is
    F = Fe + Fm = Q(E + u X B)

    The Lorentz force can also be written in terms of Newton’s law such that
    F = ma = m (du/dt) = Q(E + u X B)

    ∴ Since the electron is stationary, acceleration equals zero and the so the electron does not experience a Lorentz Force.
  2. jcsd
  3. Apr 21, 2012 #2


    User Avatar
    Science Advisor

    Well, I not sure I like "acceleration equal zero and so the electron does not experience a Lorentz Force". If an electron is constrained to be stationary, then both velocity and acceleration are 0 so the net force is 0. Just saying that something is stationary is not enough to show that a particular force, rather than the net force, is 0.

    However, in this problem, since there is no electrical field, E, and the velocity vector, u, is 0, it follows that F= Q(0+0x B)= 0 and, for that reason, there is no Lortentz force.
  4. Apr 21, 2012 #3
    Thank you HallsofIvy!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook