What Are the Key Differences Between Electron Volts and Volts in Physics?

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Discussion Overview

The discussion centers around the differences between electron volts (eV) and volts (V) in physics, exploring their definitions, relationships, and implications in the context of energy and electric potential. Participants express confusion over the terminology and seek clarification on how these units relate to each other, particularly in the context of fusion power and nuclear reactions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants clarify that the electron volt is a unit of energy distinct from joules, although they can be converted between each other.
  • One participant asserts that one eV is the energy gained by an elementary charge when it moves through a potential difference of one volt.
  • There is a discussion about the relationship between watts, joules, and electron volts, with some participants proposing that 1.6 x 10-19 watt-seconds equals one electron volt.
  • Another participant expresses curiosity about the energy yield of proton-proton fusion reactions, linking it to the concept of electron volts.
  • Some participants emphasize the importance of understanding that eV is a unit of energy and not a unit of electric potential.

Areas of Agreement / Disagreement

Participants generally agree on the basic definitions of electron volts and volts, but there is some disagreement and confusion regarding their relationships and conversions, particularly in the context of energy calculations related to nuclear reactions.

Contextual Notes

Some statements made by participants involve assumptions about the relationships between energy units and may depend on specific definitions or contexts that are not fully resolved in the discussion.

Stephanus
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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.
https://en.wikipedia.org/wiki/Electronvolt
In physics, the electronvolt[1][2] (symbol eV; also written electron volt) is a unit of energy equal to approximately 160 zeptojoules...

Volt
https://en.wikipedia.org/wiki/Volt
Voltage, electric potential difference, electric pressure or electric tension (denoted ∆V or ∆U) is the difference in electric potential energy ...

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.
Thanks
 
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Stephanus said:
1. Electron Volt Unit is Joule?
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.

Stephanus said:
3. Watt * Second = Electron Volt?
No, 1 W s = 1 J

Stephanus said:
4. Watt / Ampere = Volt (this I think I have known long ago)?
Yes.
 
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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.
 
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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.
DaleSpam said:
Stephanus said:
3. Watt * Second = Electron Volt?
No, 1 W s = 1 J
In physics, the electronvolt is a unit of energy equal to approximately 160 zeptojoules (symbol zJ) or 1.6×10−19 joules...

So, I think...
3. 1.6x10-19 Watt * second = One Electro Volt
or
One Watt applied for 1.6x10-19 second = One Electro Volt

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/procyc.html

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.

Thanks
[EDIT: 1 Kg H + 1 Kg H -> 2.4 x 1015 joules]
 
PietKuip said:
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.
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.
 
Stephanus said:
So, I think...
3. 1.6x10-19 Watt * second = One Electro Volt
or
One Watt applied for 1.6x10-19 second = One Electro Volt
Yes.
 
PietKuip said:
One eV is the energy that an elementary charge gets when it traverses a potential difference of one volt.
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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