Why are magnetic feilds formed from an electric current?

Click For Summary

Discussion Overview

The discussion revolves around the formation of magnetic fields from electric currents, exploring the underlying mechanisms and implications. Participants also touch on the relationship between electric currents and changing magnetic fields, as well as the conceptual understanding of these phenomena.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that the formation of magnetic fields from electric currents can be explained through Lorentz contraction, where differences in contraction between moving electrons and stationary positive cores lead to a net charge density that constitutes a magnetic field.
  • Another participant questions why the reverse process, where electric currents are generated by changing magnetic fields, is not also considered, highlighting its common application in power generation.
  • A further contribution describes a specific experimental setup involving a coil of AC current and a copper ring, arguing that the induced current in the copper ring is significantly greater than the primary current, despite the absence of a magnetic field in the copper itself.
  • Some participants express difficulty in visualizing the described experimental arrangement of the two rings, seeking clarification on their placement and relationship.
  • One participant raises a question about the lack of direct interaction between magnetic and electric forces, suggesting a deeper inquiry into the fundamental nature of these forces.
  • Another participant emphasizes the overarching question of "why" these phenomena occur, indicating a desire for a more profound understanding.

Areas of Agreement / Disagreement

Participants express a range of views on the mechanisms behind magnetic fields and their relationship with electric currents, with no consensus reached on the explanations provided. The discussion remains unresolved with multiple competing perspectives presented.

Contextual Notes

Participants' arguments rely on various assumptions about the nature of electric and magnetic fields, and the discussion includes unresolved questions about the interactions between these forces.

Jamez
Messages
19
Reaction score
0
Why are magnetic fields formed from an electric current? and why does the field occur in an anticlockwise direction?
 
Physics news on Phys.org
-A neutral current carrying wire is usually more or less electricaly neutral
-Relativity says objects contract in their direction of motion (lorentz contraction)
-If you move wrt the wire their is a diffence in contraction between the moving electrons in the wire and the positively charged cores standing still!
-This difference in contraction means a difference in charge density
-This net charge density constitutes an electric field we call a magnetic field

This accounts for the magnitude (the faster you move the larger the contraction) and direction (the contraction is only in the direction of motion) of the magnetic field.
 
Jamez said:
Why are magnetic fields formed from an electric current? and why does the field occur in an anticlockwise direction?

Just out of curiosity, how come you are not puzzled by the reverse process? Why not ask why electric currents are formed by changing magnetic fields? This is very commonly used in power stations to generate electric currents.

Zz.
 
ZapperZ said:
...Why not ask why electric currents are formed by changing magnetic fields? ...Zz.
Even better (MHO):

Consider a coil of 10 "primary turns" of AC current on a highly permeable iron (permalloy is better) ring with relatively large diameter to minor diameter thru the iron. Almost all of the magnet field remains inside the iron of the ring.

Now imagine a single turn copper ring of wire a little thinner than the iron cross section, but with the same major diameter as the iron ring. Furthermore imagine that the plane of copper ring is perpendicular to that of the iron ring and one part of the copper ring passes thru the center of the iron ring. That is the two circular rings are topographically joined.

There is essentially zero magnet field where there is any copper, yet the secondary loop (the copper ring) has current induced in it approximately 10 times greater than the primary current in the 10 turns!

Don't tell me any thing about "magnetic lines of force" cutting thru the copper ring. Even Faraday, who invented the concept of "line of force/ field," knew they were not real, just a convenience to aid thinking. Remember, no part of the copper ever has any significant magnetic field near it!

Who said classical physics did not have mysteries just as good as a single photon going two separate slits!
 
Last edited:
I'm trying to figure out what you're saying here, but I can't visualise the placement of the two rings...
 
cepheid said:
I'm trying to figure out what you're saying here, but I can't visualise the placement of the two rings...
They are linked, like two links of a chain. Both are circles of the same size. The planes of the ring are perpendicular and each passes thru the center point of the other's circle. Hope that helps - I can't stated it any more clearly.
 
If all that is true then why is it that magnetic forces and electric forces don't interact with each other directly ?
 
Last edited:
I think he's asking the big question of, "WHY"
 

Similar threads

High School Thought Experiment on Charge Carriers and Electrical Conduction
  • · Replies 3 ·
Replies
3
Views
1K
Undergrad Does a time varying magnetic field in vacuum produce electric field or not?
  • · Replies 7 ·
Replies
7
Views
2K
Undergrad The difference between calculating energy from 1 vs. 2 magnets?
  • · Replies 3 ·
Replies
3
Views
1K
High School Magnetic field produced by an electric current
  • · Replies 5 ·
Replies
5
Views
2K
High School Why Does My Toaster Hum Due to AC-Induced Magnetic Forces?
  • · Replies 22 ·
Replies
22
Views
3K
High School Circular motion as a result of the Lorentz force
  • · Replies 11 ·
Replies
11
Views
3K
Undergrad Is the magnetic field from this current rotationally symmetric?
  • · Replies 12 ·
Replies
12
Views
2K
High School A question about induced current in LC circuits
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Induced electric fields and induced magnetic fields confusion
  • · Replies 9 ·
Replies
9
Views
4K
Undergrad Why Doesn't Electric Force Cause Wires to Move?
  • · Replies 15 ·
Replies
15
Views
3K