「在磁場運動中的電子受力」是否等價於「磁場的改變產生電場」？

In classical electromagentic theory, the magnetic force (i.e. Lorentz force) acting on a moving electron in a magnetic field can be explained by the interaction of magnetic fields respectively produced by the moving electron with the (applied) steady magnetic field.

For example, suppose the steady field is pointing vertically downward, an electron is moving in direction into the paper. Accoding to classical electromagentic theory, this is equivalent to a current flowing in direction out of the paper. A current in such direction produces magnetic field with circular field lines centered at current. You may then visualize that the interaction of these (counterclockwise) circular magnetic field lines and the applied steady field produces a resulant field with strong intensity to the left hand side of the electron and weak intensity to the right hand side. The difference in field intensity thus forces the electron to move towards the right. This is the origin of magnetic force.

But classical electromagentic theory cannot explain why a flow of charge (or current) produces magnetic field.

On the other hand, if the magnetic field is moving but the electron is stationary, field lines will cut across the electron. By theory of electromagentic induction, cutting of field lines causes an induced force pushing the electron to move (i.e. an induced current). This can be explained by the relative motion of electron with respect to the field. The magnetic force (Lorentz force) produces on the electron causes it to move.

(to be continued on "opinion (意見)" as word limit is exceeded)

2012-02-16 00:43:09 補充：
(cont'd)...
There is deficiency in classical electromagentic theory in explaining some physical phenomena, as electric and magnetic fields are regarded as fields of different nature. However, modern theories, such as Relativity, throw new sight on the two fields.

2012-02-16 00:53:32 補充：
There is deficiency in classical electromagentic theory in explaining some physical phenomena, as electric and magnetic fields are regarded as fields of different nature. However, modern theories, such as Relativity, throw new sight on the two fields.

2012-02-16 00:53:58 補充：
You may refer to the article on the following web-page, which is highly recommended for reading,

http://galileo.phys.virginia.edu/classes/252/rel_el_mag.html

2012-02-16 00:54:55 補充：
The article, using Relativity theory, shows that magnetic field is indeed electric in nature when observing in another frame of reference.

2012-02-16 00:55:08 補充：
It conculdes that "...whether a particular force on an actual particle is magnetic or electric, or some mixture of both, depends on the frame of reference."