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EPE and mass of ion

  1. Jun 15, 2015 #1
    1. The problem statement, all variables and given/known data
    An ion, starting from rest, accelerates from point A to point B due to a potential difference between the two points. Does the electric potential energy of the ion at point B depend on it's mass?

    2. Relevant equations
    $$\Delta EPE = q \Delta V$$
    $$[J]=[C\cdot \frac{J}{C}]$$
    $$[J]=[N\cdot m]=[\frac{kg\cdot m^2}{s^2}]$$

    3. The attempt at a solution
    As can be seen in the third equation, the unit of EPE, [J] is given by it's mass [kg]. So the answer should be yes? Why is it not?
  2. jcsd
  3. Jun 15, 2015 #2


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    Gold Member

    Look at equation 1

    " $$\Delta EPE = q \Delta V$$ "

    Does the EPE here depend on mass?
  4. Jun 15, 2015 #3
    Yes, since EPE depends on V and V depends on mass.

    $$[V]=[\frac{J}{C}]=[\frac{N \cdot m}{C}] = [\frac{kg \cdot m^2}{C\cdot s^2}]$$
  5. Jun 16, 2015 #4


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    Who says it depends on mass? just because it includes kg in the units doesn't mean it depends on mass. If V=5 JC-1 everywhere, it doesn't matter how much you weigh... it's still 5.
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