Why it's (1/2)? [Electric Potential Energy]

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SUMMARY

The discussion centers on the formula for electric potential energy, specifically addressing why the expression is represented as 1/2 [qiVi] instead of simply qiVi. The reasoning provided clarifies that including both terms \(\frac{q_1q_2}{r_{12}}\) and \(\frac{q_2q_1}{r_{21}}\) results in double counting the same pair of charges. Therefore, the factor of 1/2 is necessary to accurately represent the potential energy between two point charges.

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Antonius
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My question is, why it's 1/2 [qiVi]? Shouldn't it just be qiVi?

Thank you ...
 
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You want to count "pairs"...
That is, if you include both [itex]\frac{q_1q_2}{r_{12}}[/itex] and [itex]\frac{q_2q_1}{r_{21}}[/itex], you are counting the same "pair" twice.
 
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robphy said:
You want to count "pairs"...
That is, if you include both [itex]\frac{q_1q_2}{r_{12}}[/itex] and [itex]\frac{q_2q_1}{r_{21}}[/itex], you are counting the same "pair" twice.
Oh I see,
 

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