Page 51 - Maxwell House
P. 51

BASIC EQUATIONS OF MACROSCOPIC ELECTRODYNAMICS                           31


                                                           ∘  =              (1.49)
                          0
                                     Now, we can populate 3  Maxwell’s equations as well the new
                                                        rd
                                     residents   ,      and    into the basement of Maxwell’s
                                                          0
                   q                 House,  as shown in Figure 1.6.11a. Use the fact that the charge
                   qv       -        conservation law must be fair for any charges we can get the
                                     conservation law and continuity equation for magnetic charges
                                     using (1.8) – (1.10) as

                                                                         
                                                     = ∯    ∘  = −         (1.50)
                                                     
                0                                                    
                                                                   
                                                            ∘    +   = 0              (1.51)
                  Figure 1.6.11b                                   
                Maxwell’s House      The relationship (1.51) is incorporated in Maxwell’s House
                                     basement, as shown in Figure 1.6.11b.
            1.6.14  Magnetic Lines of Force
            The images of the magnetic field distributions can be no less useful and beautiful than the









                                         a)                      b)             c)
                             Figure 1.6.12 Magnetic inductance field distribution

            inductance distributions in Figure 1.6.12 like around a) metal rings with currents, b) the Earth,
            and c) two coplanar bar magnets.

            1.6.15  Vector of Magnetic Field Strength. 2  Maxwell’s Equation
                                                  nd
            Come back to Lorentz’s force equation    = Δ ( +  x ) and consider the cross product
                                                    
                                                  x    = Δ ( x  +  x ( x ) )         (1.52)
                                                           
                                      For the sake of simplicity, assume that the charge carried by
                                      sensor #3 moves with speed  in direction perpendicular to the
                                      magnetic vector B, as shown in Figure 1.6.13.
                                      It is  evident  from this  figure that  x ( x ) = − .
                                                                                     2
                                      Therefore, the right-hand side of (1.53) can be rewritten as
              Figure 1.6.13 Triple cross
                product  x ( x )           Δ ( x − ) =
                                                                  2
                                                         
                                    1       2        Δ     2
                               Δ �  x −  � =  �  x  − �          (1.53)
                                 
                                              0
                                                     2
                                    0              0    2
                 2    1   is the speed of light. In order to undo the dependence of the B-vector in (1.53)
            Here  =
                      0  0
            from the permeability   we introduced a new vector H as
                               0
                              =     [(kg A  s ) (m kg  A  s ) = A m ]     (1.54)
                                            −1
                                                                      −1
                                                             −2
                                                          −2
                                               −2
                                   ⁄
                                                  ⁄
                                     0
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