Electric charges moving and magnetic field

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Discussion Overview

The discussion revolves around the relationship between moving electric charges and the magnetic fields they generate. Participants explore the conditions under which a single charge creates a magnetic field, the velocities involved, and the implications of these factors in electrical circuits.

Discussion Character

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

Main Points Raised

  • One participant questions the necessary speed of a single charge to generate a magnetic field, suggesting it might need to be around the speed of light (c).
  • Another participant provides a formula for the magnetic field generated by a moving electron, indicating a relationship involving the charge's velocity and position.
  • A participant expresses interest in calculating the magnetic field of a current using the provided formula.
  • One participant asserts that any amount of charge should produce a magnetic field, though they question the ease of detecting it.
  • A later reply clarifies that in typical electrical circuits, electrons do not move at the speed of light but rather at a much slower drift velocity, around 1 cm/sec, while the signal propagates at speeds comparable to light.
  • Another participant notes that calculating the magnetic field of a single moving charge can be complex, especially when considering acceleration and the principles of Special Relativity.

Areas of Agreement / Disagreement

Participants express differing views on the speed required for a charge to create a magnetic field and the nature of electron movement in circuits. The discussion includes both agreement on certain formulas and disagreement regarding the implications of charge movement and detection of magnetic fields.

Contextual Notes

There are limitations regarding the assumptions made about charge movement and the definitions of terms like "drift velocity" and "signal." The complexity of calculations involving Special Relativity is acknowledged but not resolved.

Who May Find This Useful

This discussion may be of interest to those studying electromagnetism, electrical engineering, or anyone curious about the behavior of electric charges and magnetic fields in various contexts.

haiha
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I know that a current creates a magnetic field and so do moving electric charges. My question is how fast a single charge moves so that it will create a magnetic field. Should its velocity be around c to make that?

Thks
 
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A moving electron creates a magnetic field B~vXE/c.
 
Oh, cool, I can calculate the magnetic field of a current by this formula as well. Thanks.
 
This is the magnetic field generated by a moving electric charge.

\vec{B} =\frac{q \vec{v} \times \vec{r}}{r^3}
 
I think that no matter how much of the charge are given, there should have a magnetic made. But whether or not it is easy to found .
is it ?
 
to answer haiha's question, typically in an electrical ckt, the electrons don't move around with speed of light..infact surprisingly it moves with a drift velocity. this is typically around 1cm/sec ! yes, electrons' drift velocity is very slow...it is the velocity of the signal that moves with speeds comparable to light( well it depends upon the dielectric co-effs etc). "signal" here roughly means the electro-magnetic field through space...
 
griefchan said:
I think that no matter how much of the charge are given, there should have a magnetic made. But whether or not it is easy to found .
is it ?
The magnetic field of a single moving charge is a tricky calculation using Special Relativity, especially if the charge is accelerating.
 

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