Is There Energy in Magnetic Fields?

Click For Summary

Discussion Overview

The discussion revolves around the concept of energy in magnetic fields, specifically questioning whether energy can be extracted from magnetic fields and the origins of that energy. The scope includes classical electrodynamics and the implications of magnetic fields in practical applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the existence of energy in magnetic fields.
  • Another participant asserts that a magnetic field in vacuum has an energy density of u0B2 and that this energy can be extracted through the movement of conductors within the field.
  • A question is raised regarding the source of the energy in the magnetic field.
  • There is a clarification about the original energy of the magnetic field, suggesting it comes from the process of establishing the magnetic field.
  • A correction is made regarding the expression for energy density, with a participant indicating it should be B2/2u0.
  • A later reply humorously acknowledges the correction while suggesting that everyone makes mistakes occasionally.

Areas of Agreement / Disagreement

Participants express differing views on the specifics of energy density and its formulation. There is no consensus on the precise nature of energy extraction from magnetic fields or the clarity of the energy source.

Contextual Notes

There are unresolved aspects regarding the definitions of energy in magnetic fields and the implications of energy conservation in the context of magnetic field interactions.

darkar
Messages
187
Reaction score
0
I am curious about is there any energy can be found / get in the magnetic field?
 
Physics news on Phys.org
Yes: in classical electrodynamics, a magnetic field in vacuum has an energy density of u0B2. This energy can be extracted. For example, a conductor moving at an angle through a magnetic field develops a potential difference between its endpoints. This can be used to run a current, thus performing work. The energy for that could only have come from the field, and indeed the resulting assembly produces a magnetic field that partially cancels the original field, maintaining energy conservation.
 
Then where is the energy come from?
 
zefram_c said:
Yes: in classical electrodynamics, a magnetic field in vacuum has an energy density of u0B2.

.

Uh...you of course meant to say energy density is B2/2u0, right zefram?

Creator :wink:
 
Indeed that's what I meant. Can't everyone take a nap in class every now and then?
 

Similar threads

Undergrad Particle field strength and sensitivity
  • · Replies 2 ·
Replies
2
Views
1K
Graduate Magnetic field produced by moving charge in operator form
  • · Replies 14 ·
Replies
14
Views
3K
High School Quantum teleportation of usable information
  • · Replies 19 ·
Replies
19
Views
2K
Undergrad What forces a magnet's field to track the rotation of the magnet?
  • · Replies 1 ·
Replies
1
Views
1K
High School What exactly is spin? Does the standard model work without spin?
  • · Replies 27 ·
Replies
27
Views
3K
Undergrad Hamiltonian of a particle in a magnetic field
  • · Replies 10 ·
Replies
10
Views
4K
High School Is Quantum Mechanics necessary for understanding electromagnetic phenomena?
  • · Replies 2 ·
Replies
2
Views
1K
High School Is it possible to apply thermodynamics to magnetic/weak/nuclear fields
  • · Replies 2 ·
Replies
2
Views
1K
Undergrad What is the energy of an atom in a magnetic trap as a function of position?
  • · Replies 6 ·
Replies
6
Views
2K
Undergrad Can an electron in a magnetic field radiate a virtual photon?
  • · Replies 3 ·
Replies
3
Views
2K