Understanding the Direction of Lorentz Force: Equation vs. Rules

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Discussion Overview

The discussion revolves around the directionality of the Lorentz force as described by Fleming's Left Hand Rule and the mathematical formulation using the cross product. Participants explore the reasons behind the fixed direction of the force in relation to the magnetic field and current, questioning whether this is a fundamental aspect of nature or a matter of convention.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions why the direction of the Lorentz force is fixed by the Left Hand Rule or the equation, suggesting that these methods do not explain the underlying reason for the directionality.
  • Another participant notes that the handedness of the force direction is related to how the direction of the magnetic field is defined.
  • A participant rephrases the question to inquire why the force is in a specific direction (F as ax) rather than an alternative direction (F = -ax).
  • One response states that the direction of the force is what is measured, implying that it is an empirical observation.
  • A participant seeks a deeper explanation for the force direction, comparing it to natural phenomena that have clear reasons behind them.
  • Another participant argues that the perceived effect is a result of coordinate choice, suggesting that the handedness is a matter of convention rather than a physical mystery.
  • A participant references an external link for further reading, indicating that additional resources may provide more context or information.

Areas of Agreement / Disagreement

Participants express differing views on whether the direction of the Lorentz force is a natural phenomenon or a result of arbitrary conventions. There is no consensus on the underlying reasons for the force's direction, and multiple competing perspectives remain in the discussion.

Contextual Notes

Participants have not resolved the assumptions regarding the nature of the handedness convention or the empirical observations related to the Lorentz force. The discussion remains open to interpretation and further exploration.

Ferruccio
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Lorentz force is explained or demonstrated using Fleming's Left Hand Rule or the Force equation using cross product.
What I'm trying to ask here is, why is the direction fixed using the Left Hand Rule or the equation? Why is the direction here and not there?

Equation and rules are the easiest way to explain the force direction, but they don't explain why.
 
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I have never heard of the left hand rule, but if you are asking why this has the handedness it does, it's all a matter of how we define the direction of the magnetic field.
 
Nope, I'm not asking about the determination of direction. I'm asking about why the direction.

Let me rephrase my question, let's say my current, I as my ay, magnetic field, B as my az, why is the force, F as ax? why not F = -ax or some other directions?
 
Ferruccio said:
why is the force, F as ax? why not F = -ax

That's what's measured.
 
Is there a reason for it, a theory behind, or it is a natural phenomenon which is inexplicable?

A reason for it as in, we can hear sound using ears, because the sound is in human audible range. It's a natural phenomenon too, but a reason to explain why.
 
You're creating an effect where there is none. Let's say we cross ay and az and get -ax. Instead of wondering "oh why the negative sign?" we say "we like positive things, so let's switch the direction of the x-axis!" So now ay cross az is ax.

That's all the handedness convention is, we're choosing our axes such that this works out. Nothing mysterious or physical about it. Just choosing coordinates.
 

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