Can someone explain the difference between Volts and Electron Volts?

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Discussion Overview

The discussion revolves around the differences between volts and electron volts, specifically addressing the relationship between voltage, charge, and energy in the context of electricity. Participants explore the definitions and implications of these units, as well as the calculations involved in converting between them.

Discussion Character

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

Main Points Raised

  • One participant expresses confusion regarding the relationship between coulombs, electrons, volts, and joules, questioning why 1 eV is not equivalent to the total energy of 1 coulomb of charge.
  • Another participant clarifies that an electronvolt (eV) is defined as the kinetic energy gained by an electron when it is accelerated through a 1 volt potential difference.
  • Several participants point out a typographical error regarding the number of electrons in a coulomb, emphasizing that 6.25 x 1018 electrons make up one coulomb.
  • A participant explains that a volt is defined as one joule per coulomb, and calculates that the energy acquired by one electron at one volt is 1.6 x 10-19 joules, thus defining one eV as this amount of energy.
  • Another participant suggests that the confusion may stem from the negative exponent in the conversion, indicating that the relationship involves dividing by the number of electrons per coulomb.

Areas of Agreement / Disagreement

Participants generally agree on the definitions of volts and electron volts, but there remains some confusion regarding the calculations and the relationships between these units. The discussion includes multiple perspectives on the source of the confusion, and no consensus is reached on a single explanation.

Contextual Notes

Some participants express uncertainty about the mathematical relationships and conversions involved, particularly regarding the use of exponents and the implications of charge and energy definitions.

synoptic
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OK,

Bear with me, I'm a mature student returning to the sciences after a 16 year break...

I'm currently reading up on electricity and cannot, for the life of me, get my head around what 'appears' to be an inconsistency. Obviously my brain isn't 'seeing' the answer properly just yet so I could do with some help.

Basically, if one coulomb has 6.25 x 10 -18 electrons and 1 volt is the potential energy required to carry out 1 Joule of work how is it that 1 eV is only worth 1.602 x 10. -19 Joules? Why not 6.25 X 10 -18 Joules?

I've read around many sites but can't get my brain to shift into the right perspective with this...

Cheers.
 
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A electronvolt is the kinetic energy a electron gets when its passed through a 1 volt electrostatic potential difference.

I don't quite follow why you think that amount of energy in relation to a joule should be the same as a electrons charge in relation to a coulomb??
 
Last edited:
By the way your exponent is off. 6.25 x 1018 electrons make up one coulomb of charge.
 
Ok, this is where I am going wrong obviously. The problem is I need to be un-confused...
 
dav2008 said:
By the way your exponent is off. 6.25 x 1018 electrons make up one coulomb of charge.

Quite right, apologies for the typo.
 
A volt is one joule/coulomb. The charge of an electron is - 1.6 x 10^-19 coulombs. The energy acquired by one electron being accelerated through a potential difference of one volt is therefore (1 volt) x (1.6 x 10^-19 coulombs) = 1.6 x 10^-19 joules. Thus one electron volt, one eV, is 1.6 x 10^-19 joules.

Hope this helps.
 
synoptic said:
dav2008 said:
By the way your exponent is off. 6.25 x 1018 electrons make up one coulomb of charge.
Ok, this is where I am going wrong obviously. The problem is I need to be un-confused...

you're on the right track. you were asking the right question in your initial post. so now ask yourself: what is the reciprocal of 6.25 x 1018 electrons/coulomb?
 
rbj wins a big fat cigar :smile:

It's nice when the obvious strikes you in the face :smile:

Cheers.
 
I think you are confused with the extra negative power, i.e from 18 to -19.

the reason is 1 divided by 6.25 gives 0.1602, and writing that in standard form gives 1.602 x 10^-1, giving you an extra negative power, so the charge is not 1.602 x 10^-18 but 1.602 x 10. -19 .
 

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