Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What happens to an electron in the electric field

  1. Feb 18, 2012 #1
    Hi,im new here. Can you explain to me what happens to the kinetic energy of an electron when it is accelerated in a uniform electric field? My guess is it will go to the positive plate and loses kinetic energy because it isdoing work against the field. Can anyone clarify this?

  2. jcsd
  3. Feb 19, 2012 #2
    Firstly, welcome.

    Why do you think that it is doing work against the field? Negative charge moving up potential is a decrease in potential energy, i.e. work is done to the electron as it is gaining kinetic energy.
  4. Feb 19, 2012 #3
    I think maybe my basic is not strong enough. Correct me if im wrong. The electric field direction is from positive to negative right? So the electron need to do work to go to the positive plate. Am i right?
  5. Feb 19, 2012 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    2018 Award

    No, electrons are negatively charged and are attracted to the positive plate. The direction the arrows in the field point in many pictures is meaningless. It could easily be the other way around and it would change nothing. It's simply that like charges repel and opposite charges attract.
  6. Feb 19, 2012 #5
    Well, not really. You may work more on the defining formulae. The formulae for field strenth is F=qE. The negativity of q would mean that F would be positive alone the negative direction of E
  7. Feb 19, 2012 #6
    Thanks for all the replies, so what happens to the kinetic energy and potential energy of it?
  8. Feb 19, 2012 #7
    Electrostatic potential decreases of course. Since there is no other force acting on the electron, all these potentials lost to kinetic. Actually, you mentioned accelerated in OP, so what's confusing?
  9. Feb 19, 2012 #8

    jim hardy

    User Avatar
    Science Advisor
    Gold Member
    2018 Award

    I have to oversimplify, get a physical picture in myhead and then build up to the mathematical explanation. I think in pictures and envy folks whose mind jumps immediately to the formula.

    If i correctly recall a physics class problem from forty++ years ago,
    However many volts are across the plates responsible for the field, as it approaches the positive plate the electron's kinetic energy approaches that many electron-volts ..

    here's a practical example that even I could follow.


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