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Electron Volt

  1. Dec 27, 2015 #1
    Dear PF Forum,
    I'm interested in the future. How mankind will benefit from fusion power. But there are some terms that I don't understand.
    Electron Volt.
    Perhaps this yes/no question will confirm my confusion.
    1. Electron Volt Unit is Joule?
    2. Volt unit is Volt? (of course)
    3. Watt * Second = Electron Volt?
    4. Watt / Ampere = Volt (this I think I have known long ago)?
    The names are confusing me.
  2. jcsd
  3. Dec 27, 2015 #2


    Staff: Mentor

    No. The eV is its own unit. The eV is a unit of energy and the J is a unit of energy, so you can convert between J and eV if you like, but they are separate units.

    No, 1 W s = 1 J

  4. Dec 27, 2015 #3
    It is like light years: not a unit of time but of distance.

    One eV is the energy that an elementary charge gets when it traverses a potential difference of one volt.
  5. Dec 27, 2015 #4
    Thanks Dale for the reply.
    Just curious, how many energy yield if we do P+P reaction. Although our technology is not adequate right now. Even the D+T heavily researched reaction still haven't produced a significant result.
    So, I think...
    3. 1.6x10-19 Watt * second = One Electro Volt
    One Watt applied for 1.6x10-19 second = One Electro Volt


    And if P+P reaction gives approximately 25 MEv, then...
    1 Kg Hydrogen +1 Kg Hydrogen will produce 25x106 x 1.6 10-19 x 6 x 1026 (number of Protons in 1 KG) = 2.4 x 1013 joules?
    I'm sorry, this should belong to Nuclear Physics question I think. But I only want to know if my understanding of this Electron Volt is correct.

    [EDIT: 1 Kg H + 1 Kg H -> 2.4 x 1015 joules]
  6. Dec 27, 2015 #5
    Yeah, I know a long time that light year is not a unit of TIME, even though some of my friends don't understand that and don't even hear about light year.
    So this Ev is not a unit of potential charge but a unit of energy.
    Okayyy, thanks.
  7. Dec 28, 2015 #6


    Staff: Mentor

  8. Dec 28, 2015 #7


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    2017 Award

    That needs to be repeated because it's the whole justification for using the eV. The fact is that all charged particles in experiments (electrons, ions) are accelerated using Electric Potentials and the energy they gain is always because of the same basic charge (e). It's an obvious unit to use when you have electrons and Volts. It confuses everyone - just once - and then it's a very friendly thing to use.
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