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Homework Help: Need help w/ understanding electric potential

  1. Sep 8, 2015 #1
    1. The problem statement, all variables and given/known data
    An electron moves from a point in space where the potential is 100 V to another point where the potential is 200 V. If it started from rest, what is its speed at the end of the trip?
    2. Relevant equations
    I'm not sure what's relevant and what's irrelevant at this point.

    3. The attempt at a solution
    I thought this had something to do with energy, found potential energy at 100 V to be 100 * 1.6E-19, but that doesn't seem to lead me in the right direction. I'm very confused with electric potential in general at the moment, can anyone suggest any resources that will explain it in such a way that even I can understand it?

  2. jcsd
  3. Sep 8, 2015 #2


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    You are on the correct track apart from two things.
    1. The electron charge is negative, not positive.
    2. You should always (always) write out the units. Saying the energy is a number without giving the units is meaningless.
  4. Sep 8, 2015 #3
    Thanks, I was able to figure it out! Once I recalled electrons were negative (maybe I shouldn't be doing this so late at night) the numbers made significantly more sense. I wrote up my original post a little hastily, but I do typically put in units. I was able to solve it using total energy calculated from its position at rest, and finding what the kinetic energy must have been given potential energy at the 200 V point in space. I was able to do the math, but I still need to spend a lot more time on the concept.

    Thanks for your help!
  5. Sep 8, 2015 #4


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    Last edited: Sep 8, 2015
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