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Maxwell's
Equations: extended formulation for moved objects
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. Maxwell's equations with possible extensions for moved bodies
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Background of coloured characters in Maxwell's equations:
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| → Maxwell's equations without moved bodies |
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NOTE 1: in English publications the operator "
rot H " etc is equivalent to " curl H "
or " Nabla x H " = " ∇ x H " |
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| → Maxwell's equations WITH moved bodies |
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| NOTE 2: partial derivatives are not identical with
the derivatives "d/dt" |
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Hermann von HELMHOLTZ
1821-1894
(father
of analogy between electrodynamics and hydrodynamics)
Helmholtz derived following formula
in his curl laws for any arbitrary vector
flux X in physics (i.e. hydrodynamics) through
a moved ( v ) and
simultaneously deformable area element:
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d X / dt = ∂
X / ∂ t
+ curl (X x v) + v div X
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This nearly complete and very important formula was the fundament for
"Lorentz' transformation equations" and
also
"Einstein's electrodynamics of moved bodies"
(well known as "special relativity theory")
etc |
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| Coulour
MEMO
&
Dash (')
entities |
- 1. Green characters are maGnetic field entities,
Red characters
are electRic field entities
- 2. rot H ≠ rot H &
rot E ≠ rot E etc, H & E are transformation
equations in the left side of Maxwell's equations
H in rot H is the dashed field
entity H' , E in rot E is the dashed field
entity E' etc (attention: "rot" = "curl")
→ It is a
fundamental difference between view points: ... moving with
the object/field or only observing this movement
→ Transformation
equations in general formulation are: E = E' = E + v
x B + ... (*) ,
H = H' = H - v x D + ...
(*)
etc
→ Transformation
equations in basic formulation: E = E' = E + v
x B & H = H' = H - v
x D (= Lorentz' Transformation)
→ The additional
field entities i.e. v x B & v x D caused by moved objects
→ ( ' ) are only
1 of 4 possible terms (*), (**)
→ Dashed entities
→ ( ' ) are related to the
moved system (i.e. space ship, rotor of a motor etc),
without ( ' ) to the system "in
rest"
→ Using only
basic Lorentz-Transformation : E' = E + v x B & H' = H - v x D -> transformed current is then J = J' = J - v r
→ As color
information is lost in black-white-copies, it's better
using dashed entities ( ' ) in transformation
equations (1*) - (4*) |
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THE NECESSITY TO APPLY TRANSFORMATION EQUATIONS ON MAXWELL'S
EQUATIONS CAN BE EASILY SEEN FROM
LORENTZ' EXTENSION OF FARADAY'S LAW CONSIDERING MOVED OBJECTS
WITH A LINEAR, UNIFORM RELATIVE VELOCITY v: |
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Based on Faraday's Law = 2. Maxwell's equation: curl
E = - ∂ B / ∂ t => Lorentz' (v x B)-extension yields: curl E' = - d B / dt = - ∂ B / ∂ t + curl (v x B)
It's definitely
clear that E' is NOT equal to E ... IF the linear, uniform relative velocity
v of the moved object is NOT equal to 0 ! In this case
the extremely simple Lorentz' transformation is => E' = E + v x B and the additional electric Lorentz' field,
caused by velocity v is => EV = v x B |
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Generally we shall state the relativity postulate as
follows (i.e. ref. to STRATTON, JACKSON, EINSTEIN etc): When
properly formulated,
the laws of physics are invariant to a transformation from
one reference system to another moving with a linear, uniform
relative velocity v: |
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Notation (A) of extended Maxwell's equations,
using dashed characters H' etc |
| 1.
Ampere-Maxwell's Law |

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(1*) |
| 2.
Faraday-Lorentz's Law |

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(2*) |
| 3.
electric Gauss' Law
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(3*) |
| 4.
magnetic Gauss' Law
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(4*) |
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| using classic electrodynamic field terms
for B, H, D, E etc work with area based
vector analysis for field theory |
(v ∇ ) B =
∇ x (B x
v) + v (∇ B) - B (∇ v)+ (B ∇) v |
( * ) |
| using superior magnetic vectorpotential A
based on B = ∇ x A with line based
vector analysis for field theory |
(v ∇) A =
- v x ∇ x A + ∇ (A ∙ v) - A x ∇ x v - (A ∇) v |
( ** ) |
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| Simple examples
for derivations and interpretations with respect to extended
Maxwell's equations: |
| ============================================================ |
| Notation (B) of extended Maxwell's equations
including material properties |
| extended Maxwell's equations (1*) - (4*),
If we are replacing the constitutive equations (5) - (7) by
the entities D, B and J
and the fields in the left sides of eq.
(1a) - (4a) by the "hidden" Lorentz' transformation
equations
![Maxwell equations with coloured entities: i.e. in the 2. equation rot E = - dB/dt (Faraday's-Lorentz' Law) with the identity rot E = curl E the special simplified Lorentz' transformation [red coloured] E = E + v x B is hidden - supposing constant non-rotational movement of bodies.](../maxwellgleichungen.gif)
As color information is lost in black-white-copies, it's
better using dashed entities (1*)-(4*)
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| 1. extended maxwell's equation (fields)
Ampere-Maxwell's Law |

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(1a) |
| 2. extended maxwell's equation (fields)
Faraday-Lorentz'-Law |

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(2a) |
| 3. extended maxwell's equation (sources)
electric Gauss' Law |

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(3a) |
| 4. extended maxwell's equation (sources)
magnetic Gauss' Law |

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(4a) |
| NOTE:
Symmetric structure
of Maxwell Equations |
This shown re-formulation
leads to a symmetric structure
of Maxwell's equations (1a), (2a), (3a) and (4a).
Similar to Dirac's suggestion constructing a set
of symmetric Maxwell equations we automatically get
both the electric charge density (r - ∇∙P)
and the magnetic charge density (-∇∙M) |
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( * ) 1. EXAMPLE for evaluation with magnetic flux density Terms
: Derivation of Faraday-Lorentz' Law
using equation ( * ) : Assuming special
conditions/restrictions (-> in literature often not
mentioned)
i.e. incompressible materials -> div v = 0, space
independent constant movements -> (B grad) v
= 0
and in magnetic fields directly from magnetic Gauss' law always
-> div B = 0 the remaining term on the
right side in equation ( * ) yields -> rot ( B x v
) = - rot ( v x B ) = - curl ( v x B
). Inserting this result in
Faraday's Law eq. (2a) or (2*) we can simply derive the extended
2. Maxwell's equation
for moved bodies:
| differential Faraday
-
Lorentz' - Law |
curl E' = - d B
/ dt = - ∂ B / ∂ t + curl (v
x B) |
(2b) |
using equation ( ** ) with same condition mentioned
above you get eq. (2b) with ∇ x A =
Nabla x A = curl A = B
The first term on the right side of this equation (2b) was
proved by Faraday, the second one by Lorentz.
NOTE: using this vector analytical formulation you get the
Lorentz-Term E = v x B automatically
!
The famous Lorentz law is therefore a (very important) vector
IDENTITY ... but not really a separate physical LAW.
.
( * ) 2. EXAMPLE for evaluation with
electric flux density Terms : Derivation of Ampere-Maxwell's
Law
using equation ( * ) : Assuming special conditions/restrictions
(-> in literature often not mentioned)
i.e. incompressible materials -> div v = 0, space
independent constant movements -> (D grad) v
= 0
and in electric fields directly from electric Gauss' law ->
div D = ρ the remaining term on the
right side in equation ( * ) yields for the cross product
-> rot ( D x v ) = - rot ( v x D
) = - curl ( v x D )
and in opposite to Faraday-Lorentz' Law in this Ampere-Maxwell's
Law an additional term v ∙ div D = v
∙ ρ
Inserting these results in Ampere-Maxwell's Law eq. (1a) or
(1*) we can derive
the extended 1. Maxwell's equation for moved bodies or
particles:
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differential Ampere
- Maxwell's - Law |
curl H' = J + d
D / dt = J + ∂ D / ∂ t + v ∙ ρ - curl (v
x D) |
(1b) |
The first term on the right
side of this equation (1b) was proved by Ampere, the third
term by Rowland,
the second term by Hertz (suggested and introduced by Maxwell),
the fourth term by Roentgen.
NOTE: using this vector analytical formulation you get the
"dualism" of Lorentz-Term H = - v
x D automatically !
The Rowland and Roentgen terms are therefore (important) vector
IDENTITIES ... but not really separate physical LAWS.
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( * ) 3. EXAMPLE: Proof of extended
1. + 2. Maxwell's equations using famous HELMHOLTZ' formula
Helmholtz derived following formula in his curl laws for any arbitrary vector
flux X in physics (i.e. hydrodynamics)
through a moved ( v ) and simultaneously deformable
area element - as a subset of ( * ) - :
| d X / dt = ∂
X / ∂ t
+ curl (X x v) + v div X
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( *** ) |
Inserting this Helmholtz' formula ( *** ) in the Maxwell equations (1a) or (1*)
and (2a) or (2*)
- prerequisiting both the same above mentioned conditions/restrictions
and X = B alternatively X = D -
we immediately get the extended Maxwell's equations (1b) and
(2b) in the 1. and 2. example !
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NOTE: using ( *** ) the extended Maxwell's
equations are derivable without any knowledge in vector analysis.
The Helmholtz' formula is ingenious and the basis for Lorentz
and Minkowski, too.
Helmholtz derived his formula visualizing - like a "mnemonics
artist" - moved and deformable geometric elements.
But nevertheless Helmholtz' d X / dt
neglects the LAST term (X ∇) v inside
(v ∇) X , refer to ( * ) and ( ** ) ! |
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