Magnetic field intensity and density

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Discussion Overview

The discussion centers on the differences between magnetic field intensity (H) and magnetic field density (B), exploring their definitions, relationships, and implications in physics. The scope includes conceptual clarification and technical explanations related to electromagnetism.

Discussion Character

  • Conceptual clarification, Technical explanation

Main Points Raised

  • Some participants propose that magnetic field intensity H is related to the sources of the magnetic field, specifically through the equation $$ \oint \vec H \cdot d \vec l = I $$, which connects H to the total current enclosed by a magnetic loop.
  • Others argue that magnetic field density B describes the effects of the magnetic field, providing examples such as the Lorentz force and induced EMF in transformers.
  • A participant suggests that B is a property of the material since it depends on the magnetic permeability of the loop.
  • Another participant clarifies that the property of the material is actually the magnetization vector M, and that B is the total effect of the source field H and the material response, expressed as $$ B = \mu _0(H + M) $$.
  • One participant requests further resources for detailed discussion on the topic.
  • A later reply indicates a personal familiarity with the topic without providing additional details.

Areas of Agreement / Disagreement

Participants present multiple competing views regarding the definitions and relationships of H and B, and the discussion remains unresolved with no consensus reached.

Contextual Notes

Limitations include potential misunderstandings of the relationships between H, B, and M, as well as the dependence on material properties and definitions that are not fully explored in the discussion.

nitishsharmabit
Hello folks,

Can anyone explain to me what is the difference between magnetic field intensity H and magnetic field density B?
 
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Hi
In the simplest terms, the magnetic field intensity H relates to the sources of the magnetic field. For example, the integrated H in a magnetic loop is related to the total current enclosed by the loop (time-independent) by the relation
$$ \oint \vec H \cdot d \vec l = I $$
This equation is true regardless of the magnetic permeability of the loop.
whereas intensity B describes effects of the magnetic field. Examples are Lorentz force on a charge moving in the magnetic field ##\vec F = q (\vec B \times \vec v) ##
and induced EMF in, say, a single winding of a transformer ## EMF = - \frac d {dt} \iint \vec B \cdot d \vec S ##
 
That means B is property of material since it depends on the magnetic permeability of the loop.
 
Well, strictly speaking, the property of the material is the magnetization vector, usually denoted as M. B is the total effect of the source field H and material response in terms of polarization M, such as ## B = \mu _0(H +M)##
 
Thanks! Can you provide me a link where it has been discussed in detail?
 
I'm a physicist, I just know it.
 

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