Why does the direction of an electric field depend on the charges present?

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Discussion Overview

The discussion revolves around the reasons behind the direction of an electric field being defined by the presence of positive charges rather than negative ones. Participants explore the historical context and conventions in physics, as well as the implications of these definitions on understanding electric fields.

Discussion Character

  • Exploratory, Historical, Conceptual clarification

Main Points Raised

  • One participant questions why the electric field's direction is associated with positive charges, noting that the force of attraction towards negative charges seems more intuitive.
  • Another participant suggests that the direction of the electric field is a matter of convention, comparing it to arbitrary language definitions, and mentions that the field can simply be reversed if a negative charge is present.
  • A historical perspective is provided, attributing the confusion to Benjamin Franklin's early theories on electricity, where he incorrectly designated the flow of electric fluid, leading to the current definitions of positive and negative charges.
  • One participant reassures that regardless of the convention used for the direction of the electric field, the underlying laws of physics remain consistent, with only a sign change in equations.
  • A participant expresses a desire for deeper understanding, indicating a preference for explanations over conventions.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the implications of the electric field's direction, with some accepting the convention while others express confusion and seek further clarification.

Contextual Notes

The discussion highlights the historical context of charge definitions and the arbitrary nature of conventions in physics, but does not resolve the underlying confusion regarding the directionality of electric fields.

caljuice
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Why does the field's direction depend on the positive charge and the not negative? If there is a positive charge and a negative, the direction of the field is the positive force of attraction (towards the negative). The theory of convention always confused me because i thought it was the electrons that move and not the protons?
 
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It's just conventional. Why do you call left-side left? That's something people decide upon in the ancient days of language, and people since then stuck to it (for simplicity sake). The same idea can be apply to the direction of the force, someone (my first guess would be Faraday) defined the direction of the E field by its positive direction. If there it is a negative charge, just switch the E field, no big deal.

Hope it helps (and I hope I understand the question properly)
 
You can blame Ben Franklin for your confusion. Before he became one of the USA's "Founding Fathers," he did some scientific investigation into electricity, specifically what we now know as "static electricity", with charged objects that attract and repel each other. He came up with the idea of an "electric fluid" that was normally distributed evenly. When you rubbed certain objects together, it transferred some of this fluid from one object to the other. One object now had an excess of electric fluid, which he called "positively charged." The other had a deficit of electric fluid, which he called "negatively charged." But he couldn't actually see which way the electric fluid flowed, so he had to guess, and designated one group of objects as "positive" and the others "negative."

It turned out that Franklin's electric fluid was what we now know as a flow of electrons. But he guessed the flow direction wrong. By that time it was too late to get everybody to switch "positive" and "negative," so we're stuck with it!
 
Hahaha, free history lesson there. (I guess my first guess was wrong, oh well).

I guess want to note: which ever way the direction of the field is base on, the laws of physics is still the same. All your equations would just be a negative sign different. So don't worry too much about it.
 
ah okay thanks. Sounds kind of lazy though. I always have to know why for things.
 

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