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

AI Thread Summary
The discussion centers on the formula for electric potential energy, specifically why it includes a factor of 1/2 in the expression qiVi. The reasoning provided is that including both terms for the interaction between two charges results in double counting the same pair. Therefore, to avoid this redundancy, the factor of 1/2 is necessary. This clarification helps in understanding the correct application of the formula in calculating potential energy. The importance of accurately counting pairs in physics is emphasized.
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 \frac{q_1q_2}{r_{12}} and \frac{q_2q_1}{r_{21}}, you are counting the same "pair" twice.
 
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robphy said:
You want to count "pairs"...
That is, if you include both \frac{q_1q_2}{r_{12}} and \frac{q_2q_1}{r_{21}}, you are counting the same "pair" twice.
Oh I see,
 
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