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: Charged particle entering velocity selector

  1. Mar 31, 2014 #1
    1. The problem
    A velocity selector consists of a parallel plate capacitor placed in an outside magnetic field (see figure). Charged particles entering the velocity selector experience an electric and a magnetic force (neglect effects due to gravity). Given is the setup in the figure below (attached)

    a) What is the direction of the magnetic force?
    b) What is the direction of the electric force?
    c) When the two forces are equal the particle will move straight through the velocity selector. Derive an expression for the speed v that fulfills this condition.
    d) What happens to particles that have a speed larger than v? What happens to particles that have a speed smaller than v?
    e) Protons move through a velocity selector with E = 2.0 · 10^5 N/C and B= 0.30 T. What is the speed of a proton that is not deflected?

    2. Relevant equations (negatives are supposed to be vectors)
    [itex]\overline{}F[/itex]B=q[itex]\overline{}v[/itex] x [itex]\overline{}B[/itex]
    [itex]\overline{}F[/itex]e = q[itex]\overline{}E[/itex]

    3. The attempt at a solution
    a) up
    b) down
    c) qVB=qE
    d)it will deflect up, it will deflect down
    e) v=(.30)/(2.0*10^5)= 1.5*10^-6 m/s

    Just want to know if I am doing this correctly

    Attached Files:

  2. jcsd
  3. Apr 1, 2014 #2


    User Avatar
    Homework Helper

    It looks correct.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted